If your air conditioner heat mode is not working, the most likely culprit is something you can check yourself in five minutes: a dirty filter or an incorrect thermostat setting. If those are fine, it gets more serious. That is when you need a licensed technician.

This guide walks through every cause in order of likelihood, from the quickest self-fix to the faults that require a professional. Before you call anyone, work through this list. For a breakdown of what each AC mode does, including heat, dry, cool, and auto, see our full modes guide.

How Heat Mode Works on a Reverse Cycle AC

Most Australian homes use a reverse cycle air conditioner, a system that both heats and cools using a refrigerant circuit. In heat mode, the unit reverses its normal operation: instead of pulling heat out of your home, it extracts heat from the outside air and pushes it inside. This works even when it is cold outside, because there is still usable heat energy in outdoor air down to around -10°C.

When heat mode is running correctly, the indoor unit blows warm air steadily and the outdoor unit pulls heat in. If yours is blowing cold air, running but not warming the room, or not switching on at all, something in that process has broken down.

Is It Actually a Fault? (Or Just the Defrost Cycle?)

Before you assume your system is broken, check one thing: is it in the defrost cycle?

In cold weather, ice can build up on the outdoor coil. To clear it, the unit temporarily reverses its operation, which means the indoor unit blows cool or room-temperature air for a short period. This is completely normal. You may also notice steam rising from the outdoor unit and hear the system running differently than usual.

The defrost cycle typically lasts between 2 and 10 minutes. Once it finishes, the unit switches back to heating and warm air resumes. If it does not switch back after 10 minutes, or if this happens every time you run heat mode, then it is not just the defrost cycle. There is an underlying issue worth investigating.

Why Your Air Conditioner Heat Mode Is Not Working: 5 Likely Causes

These causes are ranked by likelihood. Start at the top. Most problems are resolved within the first two checks.

1. Dirty or Blocked Filters

This is the most common reason a reverse cycle air conditioner stops heating effectively. Blocked filters restrict airflow through the indoor unit, which reduces the amount of warm air it can push into the room. In severe cases, the system will overheat and shut itself off as a protective measure.

Self-check: Remove the indoor unit’s filter panel (usually clips off without tools), pull out the filters, and hold them up to the light. If you cannot see light through them, they need cleaning. Rinse with warm water, let them dry fully, and refit. Run heat mode again.

2. Incorrect Mode or Thermostat Settings

The second most common cause, and the easiest to fix. The unit may be set to cool mode, fan-only mode, or the target temperature may be set below the current room temperature, which tells the system it has nothing to do.

Self-check: On your remote, confirm the mode is set to Heat (usually shown as a sun icon). Set the target temperature to at least 2 to 3 degrees above the current room temperature. For example, if the room is 18°C, set it to 21°C or higher. If the display shows a snowflake icon, the unit is in cool mode, not heat mode.

3. Outdoor Unit Blocked or Iced Over

The outdoor unit needs clear airflow to extract heat from the outside air. If the area around it is blocked by leaves, garden debris, or a fence that is too close, the system struggles to pull enough heat in. In Sydney’s cooler months, the outdoor coil can also ice up beyond what the defrost cycle can handle on its own.

Self-check: Walk outside and look at the outdoor unit. Clear any debris from around and above the unit. There should be at least 30cm of clearance on all sides. If you can see ice on the coil, turn the system off and let it defrost naturally. Do not use a heat source on it. Once thawed, run heat mode again and monitor whether icing returns.

4. Refrigerant Leak

Refrigerant is the substance that carries heat through the system. If there is a leak, the system loses its ability to transfer heat effectively. You will notice this as gradually weakening heating performance over weeks or months. The system runs but the room never quite gets warm. In some cases you may hear a faint hissing sound near the indoor or outdoor unit, or notice ice forming on the refrigerant lines.

Self-check: You cannot fix a refrigerant leak yourself. Handling refrigerants requires an ARCtick licence. If you suspect a leak, weak heating despite clean filters and correct settings, ice on the lines, or a hissing sound, stop running the system and call a technician. Continuing to run it with low refrigerant can damage the compressor. Some Fujitsu units will display a fault code when refrigerant pressure drops. Check our guide to Fujitsu fault codes and flashing lights if your unit is showing an error.

5. Faulty Reversing Valve

The reversing valve is the component that switches the refrigerant flow direction between heating and cooling. When it fails, the system typically stays stuck in one mode. The clearest sign of a faulty reversing valve: the unit cools perfectly but will not heat at all. If it can cool, the compressor and refrigerant are working. The problem is specifically the direction switch.

Self-check: There is no self-fix here. A reversing valve replacement is a technical repair that requires gas work and disassembly of the refrigerant circuit. If your unit cools fine but will not heat, this is the most likely mechanical cause. Book a diagnostic with a licensed technician.

When to Call a Professional

You have checked the filters. The settings are correct. The outdoor unit is clear. The unit is still not heating. At this point, stop troubleshooting and book a service.

Call a licensed technician if you notice any of the following:

• The unit cools normally but produces no heat at all
• Ice is forming on the refrigerant lines or outdoor coil and not clearing after a defrost cycle
• You can hear a hissing or bubbling sound from the indoor or outdoor unit
• Heating performance has gradually declined over weeks or months
• The unit displays a fault code or error light
• The system shuts off shortly after starting in heat mode

Attempting to diagnose or repair refrigerant issues or a reversing valve fault yourself risks voiding your manufacturer’s warranty and causing additional damage to the compressor. For brands like Mitsubishi, fault diagnosis requires specific tools. See our Mitsubishi air conditioning repairs page for what to expect from a service call.

Frequently Asked Questions

Why is my air conditioner blowing cold air in heat mode?

The most common reasons are the defrost cycle (normal and temporary), incorrect mode settings, or a dirty filter restricting airflow. Check your remote to confirm the unit is in heat mode and that the target temperature is set above the current room temperature. If it blows cold continuously after 10 minutes of running, clean the filters and check the outdoor unit for ice or blockage.

How do I know if my reversing valve is faulty?

The clearest sign is a unit that cools normally but produces no heat at all. If the cooling function works, the compressor and refrigerant are intact. The fault is specific to the valve that switches between modes. A reversing valve fault requires a licensed technician to diagnose and replace.

Can I fix my AC not heating myself?

You can clean the filters, check and adjust the settings, and clear the outdoor unit yourself. These three steps resolve the majority of heat mode problems. Refrigerant leaks, reversing valve faults, and any repair involving the refrigerant circuit must be handled by a licensed technician. Attempting these yourself can void your warranty and damage the compressor.

How long does the AC defrost cycle last?

Typically 2 to 10 minutes. During this time the indoor unit may blow cool or room-temperature air. The outdoor unit may produce steam. Once the defrost cycle finishes, the system returns to heating and warm air resumes. If the unit does not return to warm air after 10 minutes, or if it keeps triggering defrost cycles repeatedly, that points to an underlying fault.

Why does my AC cool fine but not heat?

A unit that cools but will not heat points specifically to the reversing valve. This component controls which direction refrigerant flows, cooling in one direction, heating in the other. A working cooling function confirms the compressor and refrigerant are intact. The fault is the direction switch, not the refrigerant circuit itself. This is a job for a licensed technician.

Still Not Heating? Book a Repair in Sydney

If it’s still not heating after working through this list, Air Max Air Conditioning services Sydney and surrounds. We carry out same-week diagnostic appointments across the region, including the Southern Highlands and Sutherland Shire.

Call us on (02) 4648 4811 or book a service online. If we can fix it, we will. If it’s still under warranty, we will tell you that too.

Air Max Air Conditioning is a licensed HVAC contractor serving Sydney, the Southern Highlands, and Sutherland Shire. All refrigerant work is carried out by ARCtick-licensed technicians.

The post Air Conditioner Heat Mode Not Working: What’s Causing It and What to Check First appeared first on Air-Max Air Conditioning Pty Ltd.

Air Conditioning Buying Guide

By Air-Max Air Conditioning
18 September 2026
9 min read

Picking an air conditioner size is one of the most important decisions in any installation. Get it wrong and you spend years with a unit that either can’t keep up or short-cycles itself into an early grave. Get it right and the system runs efficiently, keeps every corner of the room comfortable, and lasts well beyond its warranty period.

This guide covers how air conditioner sizing actually works, what size you need for each room type, and the Sydney-specific factors that most generic guides ignore.

30+

Years sizing and installing systems across Sydney

All brands

Daikin, Fujitsu, Mitsubishi, Actron, Haier & more

Free quote

Including a sizing assessment at no obligation

Same week

Appointments across Sydney metro and surrounds

Why Getting the Size Right Matters More Than You Think

Most people assume that a bigger air conditioner is always better. It is not. An oversized unit cools the room to the set temperature so quickly that it never runs long enough to remove humidity from the air. The result: the room hits 22°C but feels cold and damp, and the compressor cycles on and off far more often than it should. That short-cycling wears out the compressor years before its time.

An undersized unit has the opposite problem. It runs continuously on a hot Sydney day without ever reaching the set temperature. Your electricity bill climbs, the system degrades faster under constant load, and the room never quite gets comfortable.

Common Mistake

Choosing a unit size based on the previous owner’s unit, a neighbour’s recommendation, or the cheapest option in a given range. All three approaches ignore the specific characteristics of your room, home, and location.

How Air Conditioner kW Sizing Actually Works

Output kW vs. Input kW: What the Labels Mean

When you see a kW figure on an air conditioner label, it refers to the cooling output capacity — the amount of heat energy the unit can remove from a room per hour. This is not the same as the power it draws from the wall (input kW). A 5.0 kW cooling output unit might only draw 1.5–1.8 kW of electricity, thanks to the efficiency of the refrigerant cycle. For a full breakdown of running costs, see our guide on how much electricity an air conditioner uses.

When this guide says “you need a 5.0 kW unit,” that figure always refers to cooling output capacity.

The Basic Formula: Room Size x Climate Factor

Basic Sizing Formula

Floor Area (sqm) × Climate Factor = Recommended kW

Climate Factor: 0.15 for standard rooms | 0.20 for north/west-facing, high-ceiling, or poorly insulated rooms

This formula gives you a starting point. It does not account for ceiling height above 2.7 m, large glass surfaces, open doorways that connect spaces, or unusual insulation. Those adjustments are covered in the Factors That Change the Calculation section below.

Air Conditioner Size by Room Type

Use this table as your reference guide. All figures assume standard ceiling height (2.4–2.7 m), average insulation, and mixed orientation. Adjust up for north/west-facing rooms, high ceilings, or heavy glass.

Room Type	Room Size (sqm)	Recommended kW	System Type
Small bedroom / study	10–15 sqm	2.5 kW	Split system
Standard bedroom	15–20 sqm	2.5–3.5 kW	Split system
Large bedroom / master	20–25 sqm	3.5–5.0 kW	Split system
Living / dining room	20–35 sqm	5.0–6.0 kW	Split system
Open-plan living / kitchen	35–60 sqm	7.0–10.0 kW	Split system or ducted zone
Large open-plan / whole floor	60–80 sqm	10–14 kW	Ducted or multi-head split
Whole home (2–3 bed)	100–150 sqm	8–12 kW	Ducted system
Whole home (4–5 bed)	150–250 sqm	12–16 kW	Ducted system

These are starting estimates only — a site assessment accounts for ceiling height, insulation, orientation, and usage patterns.

Not sure which size is right for your home?

Our team provides a free, no-obligation quote and sizing assessment. We measure the space, check insulation and orientation, and give you an exact recommendation — not a generic guess.

Call 1300 207 428
Get a Free Quote

What Size Ducted Air Conditioner Do I Need?

Ducted air conditioning conditions an entire home from a single outdoor unit and one central indoor unit located in the ceiling cavity. Unlike split systems, ducted sizing is based on the total conditioned floor area, not individual rooms.

The general rule for Sydney homes:

• Up to 150 sqm: 8.0–10.0 kW ducted system
• 150–200 sqm: 10.0–12.5 kW ducted system
• 200–250 sqm: 12.5–16.0 kW ducted system
• 250+ sqm: 16.0 kW+ or a dual-zone/dual-system setup

Ducted systems can be zoned so that only certain rooms are conditioned at any given time. Zoning allows a smaller overall system to cover a larger home efficiently — the load on the system is reduced because you are never conditioning every room simultaneously.

Sydney Note

Older Sydney homes with poor ceiling insulation (pre-1990s construction) and north-facing living areas often need to size up by 10–15% compared to newer builds. Air-Max has 30 years of experience with the specific housing stock across Macarthur, Wollondilly, the Southern Highlands, and Sutherland Shire.

What Size Split System Air Conditioner Do I Need?

Split systems cool or heat a single room or zone. They are the most common choice for bedrooms, living rooms, and home offices. Each indoor unit requires its own outdoor unit (or shares an outdoor unit as part of a multi-head system).

For split systems, apply the basic formula: floor area (sqm) x 0.15 to 0.20. The most common sizes sold in Australia are 2.5 kW, 3.5 kW, 5.0 kW, 6.0 kW, and 7.1 kW. If your calculation lands between sizes, round up — it is better to be slightly oversized than continuously undersized, particularly in Sydney’s humid summers.

Factors That Change the Calculation

Ceiling Height (Above 2.7 m Adds Load)

Standard ceiling height is assumed to be 2.4–2.7 m. For every 30 cm above 2.7 m, add approximately 10–15% to your base kW figure. A room with 3.0 m ceilings has roughly 10% more air volume to condition than the same floor area at standard height. High-pitched ceilings in older Queenslander-style homes or new builds with feature ceilings often require one size up.

Insulation Quality and Window Exposure

Poor ceiling insulation is the single biggest variable that drives undersizing complaints. A room with no ceiling insulation can absorb 30–40% more heat in summer than the same room with quality insulation. Large west-facing windows with no external shading add significant solar load — a double-glazed, north-facing room with an external blind is a very different sizing problem to a single-glazed, west-facing room with no shade.

North/West-Facing Rooms in Sydney’s Climate

Sydney sits in a warm-temperate to humid-subtropical climate band. North and west-facing rooms receive direct afternoon sun during the hottest part of the day. West-facing bedrooms in particular can hold heat for hours after sunset. For these rooms, always apply the 0.20 factor rather than 0.15, and consider whether external shading (blinds, awnings, shade sails) is possible — external shading is significantly more effective than internal curtains at reducing solar heat gain.

Oversizing vs. Undersizing: The Real Costs of Getting It Wrong

Issue	Oversized Unit	Undersized Unit
Temperature comfort	Reaches set temp quickly but room feels damp	Never quite reaches set temperature on hot days
Humidity control	Poor — short cycle doesn’t remove moisture	Better — longer run time removes humidity
Running costs	Higher due to inefficient short-cycling	Higher due to continuous operation
Compressor wear	High — frequent start/stop is hard on the compressor	Moderate — continuous operation is less damaging than cycling
System lifespan	Shorter — compressor fails earlier	Shorter — continuous load accelerates wear
Purchase price	Higher upfront cost than necessary	Lower upfront, higher long-term cost

How Air-Max Calculates the Right Size for Your Home

When an Air-Max technician visits for a sizing assessment, they do not rely on the basic formula alone. They take actual measurements of each room, note ceiling heights, check insulation in the ceiling cavity (where accessible), assess window orientation and glass area, and ask about how you use each space — whether it is occupied during the hottest part of the day, whether there is heat-generating equipment like a kitchen range nearby, and whether the room connects to unconditioned spaces.

This on-site assessment is the most reliable way to get the right size. Generic calculators and online tools can only work with the information you give them. They cannot account for the specific quirks of your home, your street orientation, or the particular housing stock in your suburb.

Air-Max has been sizing and installing systems across Sydney’s Macarthur region, Wollondilly, Southern Highlands, and Sutherland Shire since 1997. We know the local housing stock, the local climate, and the specific challenges that come with older homes in these areas.

Get the right size first time.

Book a free Air-Max sizing assessment and quote. We measure your space, check your insulation and orientation, and give you an exact recommendation — across all leading brands.

Call 1300 207 428
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Frequently Asked Questions

What size air conditioner do I need for a 20 sqm room?

For a standard 20 sqm bedroom or study in Sydney, a 2.5 kW split system is the recommended starting point. If the room faces north or west, has high ceilings, or is poorly insulated, size up to 3.5 kW. These are estimates — a site assessment accounts for all variables.

Is a bigger air conditioner always better?

No. An oversized unit short-cycles — it reaches the set temperature quickly and shuts off before completing a full humidity-removal cycle. This leaves the room feeling cold but clammy, and puts extra wear on the compressor. An undersized unit runs constantly and never quite reaches the set temperature. Getting the size right is more important than going bigger.

Can I use one ducted system for a whole house?

Yes. A ducted system can condition an entire home from one outdoor unit and one central indoor unit. The system is sized based on the total conditioned floor area, not individual rooms. Zoning allows you to control which rooms are active. A 10–14 kW system covers most Sydney homes up to around 200–250 sqm.

What size air conditioner do I need for a bedroom?

A standard bedroom of 10–15 sqm typically needs a 2.5 kW split system. A larger master bedroom of 15–20 sqm may need 3.5 kW, especially with ensuite doors and north/west exposure. A basic sizing formula is floor area (sqm) x 0.15 kW for a cool climate or x 0.20 kW for a warm or sunny room.

How do I calculate the kW I need for my living room?

Start with the floor area in square metres and multiply by 0.15 (for a standard room) or 0.20 (for a north/west-facing room with lots of glass or poor insulation). A 30 sqm living room needs approximately 4.5–6.0 kW. Open-plan spaces that include a kitchen and dining area need more — typically 7.0–10.0 kW depending on layout and orientation.

Does ceiling height affect what size AC I need?

Yes, significantly. Standard ceiling height is 2.4–2.7 m. For every 30 cm above 2.7 m, add roughly 10–15% to your kW calculation. A room with 3.0 m ceilings has approximately 10% more air volume to condition than the same room with 2.7 m ceilings. High-ceiling rooms in older Sydney homes or new builds often need one size up from the basic estimate.

How do I know if my current air conditioner is the right size?

Signs your unit is undersized: it runs continuously on hot days but never reaches the set temperature; the room is cool near the unit but warm elsewhere. Signs it is oversized: it reaches the set temperature very quickly, cycles on and off frequently, and the room feels humid even at a comfortable temperature. An Air-Max technician can inspect your existing unit and advise whether it is appropriately sized for the space.

Air-Max Air Conditioning

Locally owned and operated since February 1997. Serving Sydney’s Southwest, Macarthur, Wollondilly, Southern Highlands, and Sutherland Shire. All technicians are ARCtick licensed and authorised installers for Daikin, Fujitsu, Mitsubishi, Actron, Haier, Carrier, Braemar, and Brivis. Call 1300 207 428.

The post What Size Air Conditioner Do I Need? The Complete kW Calculator Guide for Australian Homes appeared first on Air-Max Air Conditioning Pty Ltd.

Air Conditioner Troubleshooting

By Air-Max Air Conditioning
18 September 2026
8 min read

Your air conditioner smells. Something is coming out of the vents that definitely was not there before. Before you call anyone or start pulling the unit apart, the smell itself tells you most of what you need to know.

Different odours point to different problems, and knowing which is which can save you time, money, and in some cases, keep you and your family safe. In our 30+ years servicing air conditioning systems across Sydney, the calls we get about smells almost always fall into one of five categories. This guide covers all of them.

30+

Years serving Sydney homes and businesses

ARCtick

Licensed technicians for all refrigerant work

All brands

Daikin, Fujitsu, Mitsubishi, Actron, Haier & more

Same week

Appointments across Sydney metro and surrounds

Is the Smell Normal or a Warning Sign?

A brief, faint smell when you first turn the system on after a long break is often harmless. Dust settles on the coil and in the ducts during the off-season, and it burns off quickly once the system runs for a few minutes. That should disappear within 5 to 10 minutes.

What is not normal: a smell that persists, a smell that gets stronger over time, or any smell you would describe as burning, chemical, fishy, or like gas. Those need attention now, not later.

Quick Smell Diagnostic Guide

Use this table to identify your problem before you read further. If you know what your system smells like, jump straight to the relevant section below.

Smell Type	Most Likely Cause	Urgency	DIY or Pro?
Musty / mouldy	Mould on evaporator coil or in drain pan	Low — fix soon	DIY Start then Pro
Fishy / burning plastic	Overheating electrical components or wiring	High — act now	Pro Only
Vinegar / sour	Bacteria build-up on evaporator coil	Medium — book a service	DIY Start then Pro
Gas / chemical / sweet	Refrigerant leak	High — turn off now	Pro Only
Cigarette / stale smoke	Smoke absorbed into filters and coil	Low — but needs attention	DIY Start then Pro
Rotten egg / sulphur	Dead animal in ducts (rodent or bird)	Medium — book promptly	Pro Only
Exhaust / oily fumes	Fluid leaking onto hot components	High — turn off	Pro Only

Musty or Mouldy Smell: What It Means

This is the most common air conditioner smell, and it is especially prevalent in Sydney where humidity levels can sit above 70% for weeks at a time. If your system smells like a damp towel or a basement, mould is almost certainly the culprit.

What Causes Mould in an Air Conditioner?

Your air conditioner removes moisture from the air as part of the cooling process. That moisture is supposed to drip into a drain pan and flow out through a condensate drain line. When any part of that process is disrupted, water sits still, and mould grows.

Common causes include:

• A blocked or slow condensate drain line
• A cracked or overflowing drain pan
• Dirty evaporator coils where moisture and dust combine
• Not running the system enough — mould thrives when coils stay damp and dark
• Clogged return air filters restricting airflow across the coil

Worth Knowing

Ducted systems are more susceptible to mould than split systems because the ducts themselves can accumulate moisture. If the musty smell comes from multiple rooms or gets worse when the fan runs, the ducts may need cleaning, not just the indoor unit.

How to Fix a Musty-Smelling Air Conditioner

Start with the filters. Dirty filters restrict airflow and trap moisture, which accelerates mould growth. Remove them, rinse under water, let them dry fully before reinstalling. Many homeowners are surprised how much this alone helps.

Next, run the fan-only mode (not cool, just fan) for 30 to 60 minutes. This dries out the evaporator coil and discourages further mould growth. Make this a habit at the end of summer.

If the smell persists after filter cleaning and a fan-dry cycle, book a professional service. A technician will clean the evaporator coil with an antimicrobial treatment, flush the drain pan and condensate line, and identify any structural reasons moisture is accumulating.

Unusual smell coming from your vents?

Our technicians diagnose and fix odour issues same week across Sydney. No guesswork. Real equipment on every visit.

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Fishy or Electrical Burning Smell: The Warning Signs

A fishy smell from your air conditioner is not what it sounds like. It is not related to water or drains. It is an electrical smell, and it means something is overheating inside the unit.

Why This Is a Safety Warning

Plastic components, capacitors, and electrical wiring all emit a fishy or burning plastic odour when they overheat. This smell indicates that insulation is breaking down or that a component is on the verge of failure. Left unchecked, overheating electrical parts are a fire risk.

The same applies to a sharp burning smell or a smell of hot metal or rubber. These are all electrical warning signs.

Act Immediately

Turn the unit off at the isolator switch and do not restart it. Do not attempt to inspect the electrical components yourself. Call a licensed technician before running the system again.

What to Do Immediately

1. Turn the air conditioner off at the wall isolator switch or circuit breaker — not just via the remote.
2. Do not turn it back on, even to “test” whether the smell is still there.
3. Check whether you smell burning in the area around the indoor or outdoor unit.
4. Call a licensed air conditioning technician — describe the smell when you book so they can bring the right diagnostic equipment.

In our experience, fishy or burning smells usually come from a failing capacitor, a motor winding that is shorting, or wiring that has been damaged by pests or age. All of these are repairable, but they need to be assessed before the unit runs again.

Vinegar or Sour Smell from Your Air Conditioner

If your system smells like vinegar, white wine, or something vaguely acidic, the cause is almost always bacterial growth on the evaporator coil. This is different to mould, which produces that damp, musty odour. Bacteria produce organic acids as they grow, which is why the smell has a sharp, sour quality.

Bacteria on the Evaporator Coil Explained

The evaporator coil sits behind your indoor unit’s front panel. Warm, humid air from your room passes over it constantly. That combination of warmth, moisture, and dust creates an environment where bacteria multiply quickly, particularly in Sydney summers.

Running the system hard during humid months and then leaving it dormant lets any bacteria that have started growing sit undisturbed. When you turn the system back on, you are blowing air over a coil that has had weeks or months to develop a bacterial layer.

Good to Know

Some electric motors (particularly older AC motors) can produce a faint vinegar-like smell when running. If the smell is strongest at startup and fades quickly, the motor may be the source rather than the coil. A technician can determine which during an inspection.

The fix is a professional evaporator coil clean with an antimicrobial treatment. Unlike the musty mould scenario, filter cleaning alone will not resolve a bacterial coil problem. The coil itself needs to be treated.

Gas or Chemical Smell: Act Immediately

A sweet, chemical, or ether-like smell from your air conditioner can indicate a refrigerant leak. Some people describe this as acetone or nail polish remover. Others describe a faint fishy smell — which is why refrigerant leaks are sometimes confused with electrical issues.

Refrigerant itself is colourless, but it can produce a noticeable odour at the concentrations that come from a leak inside a room. Some refrigerants also cause mild irritation to the eyes and throat at higher concentrations.

Important — Legal Requirement

Handling refrigerant in Australia requires an ARCtick licence. It is illegal to vent refrigerant to atmosphere. Do not attempt to inspect, top up, or repair a refrigerant system yourself. Turn the unit off, ventilate the room, and call a licensed technician.

Signs that a refrigerant leak may be behind the smell:

• The system is running but not cooling as effectively as usual
• Ice forming on the indoor unit or copper pipes
• A hissing sound near the indoor or outdoor unit
• Higher than usual electricity bills with reduced cooling output

All Air-Max technicians hold ARCtick licences and carry refrigerant leak detection equipment on every service vehicle. If you suspect a refrigerant leak, call us before running the system further.

Cigarette or Stale Smoke Smell from the Vents

Air conditioners recirculate indoor air. If someone smokes indoors, the unit draws that air through the filters, over the coil, and back into the room. Over time, the nicotine, tar, and other compounds in cigarette smoke bind to the filter fibres and to the evaporator coil surface.

When the system runs, it reheats those compounds and blows them back through the vents. The result is a persistent stale smoke smell, even in rooms where no one has smoked for weeks.

The fix has two parts. First, replace the filters — washing them is often not sufficient to fully remove bound smoke residue. Second, book a professional coil clean with a deodorising treatment. The coil holds the bulk of the embedded odour, and a surface clean with the right chemical agent is the only way to shift it effectively.

If you have recently bought a property where the previous occupants smoked, budget for a full service before you run the system.

Quick-Fix Steps You Can Do at Home

Before calling a technician, work through these steps in order. They resolve a significant proportion of mild smell complaints and cost you nothing.

1. Clean the filters. Remove the return air filters from the indoor unit. Rinse them under lukewarm water, let them dry completely in a shaded spot, then reinstall. Do not reinstall damp filters.
2. Run fan-only mode for 30–60 minutes. This dries the evaporator coil and helps disperse any trapped odour from the ducts. Do this with windows slightly open to ventilate.
3. Check the area around the indoor unit. Look for visible mould on the unit casing or around the vents. Wipe accessible surfaces with a diluted white vinegar solution and a microfibre cloth.
4. Check your drain pan if accessible. Some split systems allow you to open the front panel and see the drain pan. If there is standing water, the condensate drain line may be blocked — this is a job for a technician.
5. Check the outdoor unit. Clear any debris (leaves, dirt, vegetation) from around the outdoor condenser unit. Restricted airflow to the outdoor unit can cause a burning or hot smell at startup.

If the smell persists after working through these steps, or if the smell is fishy, burning, or chemical, stop here and call a technician. Do not run the system repeatedly hoping it will clear.

When to Call a Licensed Technician

Some smells are a DIY-start situation. Others are not. Here is the clear line:

Call a technician if:

• The smell is fishy, burning, or smells like hot plastic or metal
• The smell is chemical, sweet, or reminiscent of acetone or ether
• The smell is accompanied by reduced cooling, ice on the unit, or unusual noises
• The musty or vinegar smell persists after you have cleaned the filters and run fan mode
• You can see mould inside the unit or on the duct vents
• The smell is coming from a ducted system across multiple rooms

Air-Max technicians service split systems, ducted systems, multi-head systems, and commercial setups across Sydney, the Macarthur region, Wollondilly, Southern Highlands, and Sutherland Shire. We carry cleaning and coil treatment equipment on every vehicle so we can usually resolve odour issues in a single visit.

How to Prevent Air Conditioner Smells Long-Term

Prevention is significantly cheaper than a callout. These habits make a real difference:

• Clean your filters every 4 to 6 weeks during periods of heavy use. Dirty filters are the single most common cause of odour complaints.
• Run fan-only mode for 30 minutes after heavy cooling sessions. This dries the evaporator coil and prevents the damp conditions mould and bacteria need to establish.
• Book an annual service. A professional clean includes coil treatment, drain pan flush, and a full system check. For heavy users, a service every six months is better. Learn more about our Air Conditioning Maintenance service.
• Keep your return air vents clear. Furniture, curtains, and rugs blocking return air vents force the system to work harder and create warm, still air pockets where mould can develop.
• Act on smells early. A mild musty smell caught early is a filter clean. Left for six months, it becomes a mould remediation job. The sooner you address it, the cheaper the fix.

For tips on filter cleaning, see our guide on Cleaning Your AC Filter. And if your system is showing other signs of trouble, our Air Con Servicing Sydney page covers what a full service includes.

Book a service and get your air conditioner smelling clean again.

Same-week appointments. All brands. Sydney metro and surrounds. Our team carries cleaning and coil treatment equipment on every visit.

Call 1300 207 428
Get a Free Quote

Frequently Asked Questions

Why does my reverse cycle air conditioner smell when I turn it on?

A brief smell at startup is usually dust or mould that has settled on the evaporator coil during the off period. It should clear within 5 to 10 minutes. If it does not, clean your filters and run fan-only mode for 30 minutes. Persistent startup smells that don’t clear need a professional coil clean.

Why does my ducted air conditioner smell musty?

Musty smells from ducted systems are almost always caused by mould in the ducts, on the evaporator coil, or in the drain pan. Sydney’s humidity makes this common. If the smell comes from multiple vents, the ducts themselves may need cleaning in addition to the indoor unit. A professional duct clean and coil treatment is the most effective fix.

What does a refrigerant leak smell like?

Refrigerant leaks can produce a faint sweet or chemical smell, sometimes described as ether or acetone. Some people also notice a faint fishy quality. If you suspect a leak, turn the unit off and call a licensed ARCtick technician. Refrigerant handling is legally restricted in Australia, and a leak that continues can damage the compressor.

Can I clean my air conditioner myself to remove the smell?

You can clean the return air filters yourself — remove them, rinse with water, let them dry fully, and reinstall. This often resolves mild musty smells. For evaporator coil cleaning, drain pan treatment, or duct cleaning, you need a professional. DIY coil sprays are available but are significantly less effective than a proper service with the right equipment.

How do I get rid of a musty smell from my air conditioner?

Start by cleaning your filters. Then run fan-only mode for 30 to 60 minutes to dry the evaporator coil. If the smell continues after both steps, book a professional service. The technician will clean the coil with an antimicrobial treatment, flush the drain pan, and check the condensate drain line for blockages.

Why does my air conditioner smell like fish or burning?

A fishy or burning smell from an air conditioner almost always means overheating electrical components — plastic insulation, capacitors, or wiring. This is a safety issue. Turn the unit off at the isolator switch immediately and do not restart it until a licensed technician has inspected the system.

How often should I service my AC to prevent odours?

Annual servicing is the minimum for most Sydney homes. If you run your system heavily, or if the property has pets or smokers, service every six months. Regular filter cleaning every 4 to 6 weeks significantly reduces odour development between professional services.

Air-Max Air Conditioning

Locally owned and operated since February 1997. Serving Sydney’s Southwest, Macarthur, Wollondilly, Southern Highlands, and Sutherland Shire. All technicians are ARCtick licensed and authorised installers for Daikin, Fujitsu, Mitsubishi, Actron, Haier, Carrier, Braemar, and Brivis. Call 1300 207 428.

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Air Conditioning Guide

By Air Max Air Conditioning | July 21, 2026 | 6 min read

If you have been shopping for air conditioning in Australia, you have almost certainly come across the term reverse cycle. It is arguably the most important thing to understand about modern air conditioning — and once you do, it changes how you think about both heating and cooling your home. Here is a straight explanation of what it is, how it works, and why it is the dominant choice for Australian homeowners.

What Is Reverse Cycle Air Conditioning?

Reverse cycle air conditioning is a system that can both cool in summer and heat in winter, using a single unit. The name comes from the fact that the refrigerant cycle can be reversed — so instead of only extracting heat from inside your home to cool it, the system can also extract heat from outside and bring it inside to warm the room.

Almost all modern split system air conditioners sold in Australia are reverse cycle. If you are buying or installing a new system and it has a heat mode on the remote, it is reverse cycle.

In Australia, reverse cycle is not a premium upgrade — it is the standard. The vast majority of residential split system air conditioners sold here are reverse cycle as a baseline feature.

How Does Reverse Cycle Work?

The key to understanding reverse cycle is that air conditioners do not create heat or cold — they move heat from one place to another.

Cooling Mode

The refrigerant absorbs heat from the indoor air as it passes over the indoor coil. That heat is carried to the outdoor unit, where it is expelled into the outside air. Your indoor air is returned cooled.

Heating Mode (Reversed)

The refrigerant cycle reverses direction. The outdoor coil absorbs heat energy from the outside air (even on cold days — there is always heat energy in air above zero degrees). That heat is transferred inside and released through the indoor coil, warming your room.

This is why reverse cycle is so energy-efficient. Rather than generating heat by burning fuel or using electric resistance elements, the system pumps existing heat energy from outside to inside. It can deliver 3 to 5 units of heat energy for every 1 unit of electricity consumed.

On a cold 10-degree Sydney winter morning, there is still substantial heat energy in the outside air. A reverse cycle system extracts it and delivers it inside. That is why your aircon can heat a room even when it feels cold outside.

Reverse Cycle vs Cooling-Only Air Conditioners

• Cost difference: Reverse cycle units typically cost a little more than cooling-only equivalents, though the gap has narrowed as reverse cycle has become the norm.
• Energy use in winter: A cooling-only unit cannot heat a room. A reverse cycle unit handles both, making it a genuine year-round solution for most Australian climates.
• Suitability: For Sydney and most of coastal NSW, reverse cycle is the obvious choice — winters are mild enough that the heat pump remains highly efficient throughout the season.

Reverse Cycle vs Gas Heating

• Efficiency: Reverse cycle delivers a COP of 3.5 to 6.5 — meaning 3.5 to 6.5 units of heat for every 1 unit of electricity. Gas heaters convert 70 to 90 per cent of gas burned into heat, with no possibility of exceeding a 1:1 ratio.
• Running cost: Reverse cycle heating is typically 30 to 50 per cent cheaper to run per unit of heat than ducted gas heating in Sydney.
• Cooling in summer: Gas heating provides no cooling benefit. A reverse cycle system handles both without additional equipment.
• Infrastructure: Gas requires ongoing connection, meter rental, and supply fees. Reverse cycle runs entirely on electricity, which can be offset with solar.

For ducted air conditioning installation and air conditioner repairs across Sydney, reverse cycle is what Air-Max installs and recommends for residential applications.

✓

The Key Takeaway on Gas vs Reverse Cycle

Gas heats your home by burning fuel. Reverse cycle moves heat from outside to inside using electricity. The physics of heat pumps means reverse cycle wins on efficiency — and the gap widens as gas prices rise.

Types of Reverse Cycle Air Conditioners

• Split system (wall-mounted): The most common residential option. All modern split systems from reputable brands are reverse cycle.
• Multi-head split system: Multiple indoor heads connected to a single outdoor compressor. Up to 5 zones from one outdoor unit. Available as reverse cycle across the board.
• Ducted reverse cycle: A single large unit distributes heated or cooled air through ducts and ceiling vents. All modern ducted air conditioning systems in Australia are reverse cycle.
• Cassette and concealed systems: Used in commercial or high-end residential applications. Available in reverse cycle configurations from all major brands.

Running Costs and Efficiency

Modern inverter-driven reverse cycle systems typically achieve a COP of 3.5 to 6.5 in heating mode and an EER of 3.0 to 5.5 in cooling mode.

The inverter compressor adjusts its speed continuously to match the room’s actual demand — preventing wasteful start-stop cycling and delivering stable, efficient performance.

Regular air conditioning servicing maintains these efficiency levels over time. A dirty filter or blocked coil can reduce COP significantly.

Frequently Asked Questions

Is reverse cycle air conditioning the same as a heat pump?

Yes — a reverse cycle air conditioner is a type of heat pump. The term “heat pump” describes any system that moves heat energy from a lower temperature source to a higher temperature destination using a refrigerant cycle. Reverse cycle air conditioners do exactly this, and the terms are often used interchangeably in the Australian market.

Does reverse cycle air conditioning work in cold weather?

Yes. Reverse cycle systems are designed to extract heat from outdoor air even when temperatures are low. Most modern units function efficiently down to around -10 to -15 degrees Celsius outdoors. For Sydney winters, which rarely drop below 5 degrees, reverse cycle heating performs at excellent efficiency throughout the season.

What is the difference between reverse cycle and ducted gas heating?

Ducted gas heating burns natural gas to generate heat, which is distributed through ducts. Reverse cycle moves heat energy from outside to inside using electricity. Reverse cycle can achieve 3.5 to 6.5 times the heating output per unit of energy compared to gas. Reverse cycle also provides cooling in summer; gas heating does not.

Which brands make the best reverse cycle air conditioners in Australia?

Daikin, Mitsubishi Electric, and Fujitsu are consistently rated as the top performers in Australia for reliability, efficiency, and service network. Panasonic, LG, and Samsung are strong mid-tier options. Air-Max installs and services all major brands and can advise on the best fit for your specific room size, budget, and usage pattern.

Can a reverse cycle system replace my gas heater entirely?

In most Sydney homes, yes. A correctly sized reverse cycle split system or ducted system can replace gas heating as the primary heat source, and it will also cool the home in summer. Many homeowners also remove the gas connection entirely to eliminate the daily supply charge.

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Troubleshooting

By Air Max Air Conditioning | July 21, 2026 | 7 min read

Your Rinnai air conditioner has flashed a code on the display or the remote and now will not operate. Before you call a technician, take a breath. Many Rinnai fault codes are informational — some can be cleared with a simple reset, others point to routine maintenance, and a few do require a qualified technician to attend. This guide walks through the most common Rinnai fault codes in plain English so you know exactly where you stand.

How to Read a Rinnai Fault Code

Rinnai fault codes typically appear as a combination of letters and numbers on your indoor unit’s display panel or on the remote control screen. The code format varies slightly depending on the model range, but you will generally see codes like E1, E3, F0, F1, P0, or similar two-character combinations.

When a fault occurs, the unit will usually:

• Display the fault code on the indoor unit’s LED panel or LCD remote
• Stop operating or reduce to a limited safe mode
• Sometimes flash an indicator light in a pattern corresponding to the code

Always note the exact code shown before attempting a reset. If the code returns after a reset, that information is critical for your technician to diagnose the problem efficiently.

Common Rinnai Fault Codes Explained

Below are the most frequently encountered fault codes across the Rinnai split system and ducted air conditioning range. Rinnai air conditioners are rebadged Haier/Aux units in most cases, and many codes are shared across these platforms.

Code	Meaning	What to Do	Action Required
E1	Indoor coil temperature sensor fault	Power off, wait 5 minutes, restart. If code persists, sensor likely needs replacement.	Technician
E2	Indoor ambient temperature sensor fault	Clean the filter and ensure airflow is not obstructed around the return air. Power cycle and retry.	Check First
E3	Outdoor coil temperature sensor fault	Check that the outdoor unit is not blocked or covered. Power cycle. Likely requires technician if persistent.	Technician
E4	Discharge temperature sensor fault (compressor outlet)	Do not attempt to run the system. This sensor protects the compressor from overheating. Call a technician.	Technician
E5	Outdoor ambient temperature sensor fault	Power cycle first. If it persists, sensor replacement is required by a licensed technician.	Technician
F0	Communication error between indoor and outdoor units	Check that the unit has not lost power. Inspect wiring connections at the indoor head if accessible. If not, call a technician.	Technician
F1	Indoor fan motor fault	Turn off the unit. Do not attempt to run it with a fan fault — motor damage can result. Call a technician.	Technician
F3	Outdoor fan motor fault	Check that nothing is blocking the outdoor fan (leaves, debris). Clear any blockage and retry. If it persists, technician attendance is required.	Check First
P0	High pressure protection — system pressure too high	Check outdoor unit airflow. Ensure coil is not blocked. This is a protective shutdown — running through it risks compressor damage.	Technician
P1	Low pressure protection — system pressure too low	Often indicates a refrigerant leak. Do not run the system. Contact a licensed technician immediately.	Technician
P2	Compressor overload / overcurrent protection	Power off and wait 30 minutes before restarting. If it trips again, the compressor or power supply needs inspection.	Technician
H3	High discharge temperature — compressor protection	Check outdoor unit airflow. Possible low refrigerant or dirty coil. Do not run system — contact a technician.	Technician
EE	EEPROM (memory) fault — controller board issue	Power cycle the unit. If it persists, the indoor control board likely needs replacement.	Technician
88	System initialising / power-up cycle	Normal — wait for the unit to complete its startup sequence. If it does not clear within 2 minutes, power cycle.	Normal

Important Safety Note

Fault codes related to refrigerant pressure (P0, P1), compressor protection (P2, H3, E4), or communication failures (F0) should never be overridden by repeated resets. Running an air conditioner through a protective fault can cause irreversible compressor damage, which is the most expensive component to replace. When in doubt, turn it off and call a licensed technician.

How to Reset a Rinnai Air Conditioner

A basic power cycle is the correct first step for most fault codes. Here is how to do it properly:

• Step 1: Turn the unit off at the remote or wall panel, then press the power button on the indoor unit itself if accessible.
• Step 2: Switch off the circuit breaker for the air conditioner at your switchboard. Leave it off for at least 5 minutes — not 30 seconds. Many fault resets require a full capacitor discharge.
• Step 3: Switch the breaker back on and wait for the unit to complete its startup cycle (you will usually hear a click from the indoor unit as it initialises).
• Step 4: Turn the system on using the remote and monitor whether the fault code returns within the first few minutes of operation.

If the fault code returns within a short period of operation, it is telling you the underlying problem has not been resolved. Note the exact code, stop running the unit, and book a professional air conditioning repair before running it further.

When to Reset vs When to Call

A reset is worth trying once for most non-compressor fault codes. If the code returns after a single reset, the underlying fault is real — repeated resets will not fix it and may mask an issue that causes further damage.

Which Faults Can You Fix Yourself vs Which Need a Technician?

Here is a clear breakdown of what is safe to check yourself versus what must be handled by a licensed air conditioning technician:

Safe to Check Yourself

• Dirty air filter: Remove and clean (or replace) the indoor filter. A clogged filter triggers temperature sensor errors, reduces efficiency, and can cause freeze-up events.
• Blocked outdoor unit: Clear leaves, debris, garden furniture, or anything blocking the coil or fan on the outdoor unit.
• Tripped circuit breaker: Check the switchboard and reset if tripped — this can cause communication and startup errors.
• Power cycle: As detailed above — a full breaker-off reset is appropriate as a first step for most fault codes.

Requires a Licensed Technician

• Refrigerant-related faults (P0, P1, H3): Handling refrigerant is illegal in Australia without an ARCtick licence. Do not attempt to add or check refrigerant yourself.
• Sensor replacements (E1–E5): Involves electrical components and calibration. Must be done by a qualified technician.
• Fan motor faults (F1, F3): Motor replacement and testing requires specialist tools and electrical competency.
• Compressor protection events (P2, E4): These faults require diagnosis of the entire refrigerant circuit and electrical supply before the system should be restarted.
• Control board faults (EE, F0): Board replacement and wiring work require a licensed technician and electrician where applicable.

How to Prevent Fault Codes from Coming Back

Most recurring fault codes on Rinnai air conditioners are preventable with routine maintenance. Here is what actually makes a difference:

• Clean the indoor filter every 4 to 6 weeks during periods of regular use. A dirty filter is the single most common root cause of temperature sensor errors and efficiency loss.
• Book an annual service with a qualified technician. This covers coil cleaning, refrigerant pressure check, electrical connections, and drain inspection — the same maintenance that prevents most fault code events.
• Keep the outdoor unit clear. Trim vegetation that grows around the unit and ensure at least 300mm of clearance on all sides and above.
• Do not block return air vents. Furniture, curtains, or built-in shelving blocking indoor return air causes system strain and can trigger high-temperature protection codes.

If your Rinnai system is repeatedly throwing fault codes despite regular maintenance, it may be approaching end of life or have a persistent underlying issue. An Air-Max technician can assess whether repair or replacement with a new system is the better investment.

Frequently Asked Questions

What does E1 mean on a Rinnai air conditioner?

E1 on a Rinnai unit typically indicates an indoor coil temperature sensor fault. Try a full power cycle (breaker off for 5 minutes). If the code returns, the sensor needs replacement by a licensed technician. Do not continue running the system through an E1 fault.

How do I clear a fault code on my Rinnai air conditioner?

Turn the unit off at the remote, then switch off the circuit breaker at your switchboard for at least 5 minutes. Restore power and restart. If the fault code clears and does not return, the issue was transient. If it returns within a few minutes of operation, the underlying fault needs professional attention.

What does P1 mean on a Rinnai air conditioner?

P1 is a low pressure protection code, which typically indicates the system’s refrigerant pressure has dropped below safe operating levels. This usually means there is a refrigerant leak somewhere in the system. Do not attempt to run the system — continued operation without adequate refrigerant pressure will damage the compressor. Contact a licensed technician.

Is it safe to reset a Rinnai fault code yourself?

A single power cycle reset is safe for most codes and is always worth trying first. What is not safe is repeatedly resetting the system when a code keeps returning, particularly for compressor protection codes like P0, P1, P2, H3, and E4. These codes exist to prevent catastrophic component failure — overriding them through repeated resets can result in compressor burnout, which is the most expensive repair in an air conditioning system.

Are Rinnai air conditioner fault codes the same as other brands?

Rinnai air conditioners sold in Australia have largely been rebadged Haier or Aux units, so many fault codes are shared across those platforms. However, codes can vary between model ranges and generations. Always cross-reference the fault code against your specific model’s installation manual if available. If you cannot find the manual, Air-Max technicians are familiar with the Rinnai range and can diagnose directly from the code and symptom.

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Running Costs

By Air Max Air Conditioning | July 21, 2026 | 6 min read

Your air conditioner is almost certainly the largest electricity consumer in your home. During a Sydney summer, it can account for 40 to 60 per cent of your total electricity bill. That is not a reason to sweat it out — but it is a reason to understand what you are paying for, how to calculate your costs, and where the real savings are hiding.

How Much Power Does an Air Conditioner Use?

Air conditioners are rated in kilowatts (kW) — but the capacity rating (e.g. 2.5kW, 5kW) is the heating or cooling output, not the power it draws from the wall. The electricity consumption is a separate figure, typically expressed as the input power or energy efficiency ratio (EER / COP).

As a general rule, a modern inverter split system uses roughly one-third of its cooling capacity in electricity. A 5kW cooling system typically draws around 1.5 to 1.8kW of power. Older non-inverter units are far less efficient and can draw significantly more.

The kW figure on your aircon is the cooling output, not the power bill figure. Look for the input wattage (kW) in your unit’s specifications or on the energy rating label to find what it actually draws from the grid.

Power Usage by Air Conditioner Type

Different system types draw very different amounts of power. Here is a practical comparison across the most common air conditioner types used in Australian homes:

System Type	Typical Capacity	Approx. Input Power	Estimated Cost/hr (at $0.30/kWh)
Small split system (bedroom)	2.5kW	0.7 – 0.9kW	$0.21 – $0.27/hr
Medium split system (living room)	5.0kW	1.4 – 1.8kW	$0.42 – $0.54/hr
Large split system (open plan)	7.0kW	2.0 – 2.5kW	$0.60 – $0.75/hr
Ducted system (whole home)	10 – 14kW	3.0 – 5.0kW	$0.90 – $1.50/hr
Multi-head system (3 zones)	8 – 10kW total	2.5 – 3.5kW	$0.75 – $1.05/hr
Older non-inverter split	3.5kW	1.8 – 2.5kW	$0.54 – $0.75/hr

Important Note on These Figures

These are estimates based on typical operating conditions at moderate outdoor temperatures. Real-world consumption varies with temperature, thermostat setting, insulation quality, and how hard the system has to work. Your electricity tariff also affects the dollar cost — check your bill for your actual rate per kWh.

How to Calculate Your Running Cost

You can estimate your own running cost in three steps:

• Find the input power (kW). Check the energy rating sticker on your unit or the product specifications. It will show the input wattage in kW — not the capacity.
• Multiply by hours of use. If your unit draws 1.5kW and you run it for 6 hours a day, that is 9kWh per day.
• Multiply by your electricity rate. At $0.30 per kWh, 9kWh costs $2.70 per day, $18.90 per week, or around $81 per month just for that one unit.

For a ducted system running whole-house cooling, the daily cost can easily reach $10 to $15 or more during a Sydney heatwave. Understanding this figure helps you make smarter decisions about when and how you run the system.

Quick Formula

Input kW x Hours per day x Days per month x Your electricity rate ($/kWh) = Monthly cost for that unit.

What Affects How Much Electricity Your Aircon Uses?

Two identical systems in two different homes can have wildly different running costs. These are the main variables:

Outside Temperature

The hotter it is outside, the harder the compressor works to maintain your set temperature. A 38-degree day costs significantly more to cool through than a 28-degree day at the same thermostat setting.

Home Insulation

A well-insulated home holds the cool air in. Poor insulation means the system constantly fights heat entering through the ceiling, walls, and windows. Ceiling insulation alone can reduce air conditioning costs by 20 to 40 per cent.

System Age and Condition

Older units, dirty filters, and low refrigerant all reduce efficiency. A well-maintained system runs at rated efficiency. One that has not been serviced in years can draw 20 to 30 per cent more power for the same output.

Thermostat Setting

Every degree lower on your thermostat in summer adds roughly 5 to 10 per cent to your running cost. Keeping the setting at 24 to 26 degrees rather than 20 degrees makes a real difference to your bill over a full summer.

How to Reduce Your Air Conditioning Power Bill

You do not have to choose between comfort and a reasonable electricity bill. These practical steps genuinely move the needle:

• Set the thermostat to 24 to 26 degrees in summer. The difference between 24 and 20 degrees can cut running costs by 20 to 30 per cent.
• Use timer and zone features. Only cool rooms you are actually in. Ducted systems with zone control can significantly reduce consumption versus cooling the whole house.
• Service your system annually. Clean filters, correct refrigerant, and clean coils keep the system running at peak efficiency. A dirty system works harder for the same result.
• Pre-cool before peak tariff periods. If you are on a time-of-use electricity tariff, run the system harder during off-peak periods and coast through the peak window.
• Block direct sun from windows. External blinds, block-out curtains, or shade structures on north and west-facing windows dramatically reduce heat load and cut how hard the aircon has to work.
• Consider upgrading old, inefficient units. A modern inverter unit can be two to three times more efficient than a non-inverter system from 10 years ago. The running cost savings often pay back the upgrade within a few years.

Frequently Asked Questions

How many kWh does an air conditioner use per day?

It depends on the unit size and how long you run it. A typical 5kW split system drawing 1.5kW of input power, run for 8 hours, uses around 12kWh per day. At $0.30/kWh, that is $3.60 per day or around $108 per month. Larger ducted systems used for whole-home cooling can use 30 to 50kWh per day during extreme heat.

Does running an air conditioner on a higher temperature use less electricity?

Yes. In cooling mode, the higher the thermostat setting (closer to outdoor temperature), the less work the compressor does. Setting 26 degrees instead of 20 degrees on a 35-degree day reduces the temperature differential the system has to maintain, which directly reduces power draw. A rule of thumb is 5 to 10 per cent less energy per degree higher in summer.

Is it cheaper to leave the aircon on all day or turn it on and off?

For most Australian homes, turning the system off when you leave and back on when you return is cheaper than leaving it on all day. The exception is if your home is very well insulated and the outdoor temperature does not exceed 30 degrees — in that case, maintaining a steady temperature can be more efficient. For a poorly insulated home in Sydney summer heat, turn it off.

Do newer air conditioners use significantly less power than older ones?

Yes, significantly. Modern inverter-driven systems have efficiency ratings (COP) of 3.5 to 6.5, meaning they deliver 3.5 to 6.5 units of cooling for every 1 unit of electricity. Non-inverter systems from 10 or more years ago typically have a COP of 2.0 to 3.0. That difference translates directly into lower running costs — often 30 to 50 per cent lower for the same amount of cooling.

What size air conditioner do I need for my room?

Sizing depends on room area, ceiling height, insulation, sun exposure, and climate. As a rough guide: small bedrooms (up to 20sqm) need a 2.0 to 2.5kW unit; main living areas (25 to 40sqm) typically need 5.0 to 7.0kW; larger open-plan spaces may need 8kW or more. Oversizing wastes money on a larger system and can result in short-cycling. Undersizing means the unit runs constantly and still cannot reach temperature. Get a proper load calculation before purchasing.

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Air Conditioning Tips

By Air Max Air Conditioning | July 21, 2026 | 5 min read

You are pointing your remote at the aircon, scrolling through the modes, and you spot it: a small teardrop or water droplet icon. That is Dry Mode. It is one of the most overlooked features on a modern air conditioner, and it is genuinely useful on those muggy Sydney days when the air feels thick and uncomfortable but it is not actually that hot. Understanding what it does and when to use it can save you money and make your home far more comfortable.

What Is Dry Mode?

Dry Mode is a setting available on most modern split system and ducted air conditioners. Its job is to reduce humidity in a room without aggressively cooling the air. Rather than blasting cold air to lower the temperature, it runs a gentler cycle focused on pulling moisture out of the air.

Think of it as your aircon acting like a dehumidifier. The result is air that feels less sticky and more breathable, even if the temperature reading on your thermostat does not change much.

Dry Mode does not replace cooling on a hot day. It is designed specifically for humid but mild conditions — the kind of sticky, overcast day Sydney gets regularly in autumn and spring.

How Does Dry Mode Work?

In Dry Mode, your air conditioner runs its refrigerant cycle at a low, steady pace. Here is what actually happens inside the system:

• The indoor fan slows right down. A slower fan means air passes over the cold evaporator coil more slowly, which allows more moisture to condense and drip away.
• The compressor runs at reduced capacity. It is not trying to cool aggressively — just enough to keep the coil cold enough to collect condensation.
• Moisture is removed continuously. The condensed water drips into the drain pan and exits through the condensate drain, just as it does in cooling mode — but at a gentler, more sustained rate.
• Temperature drops only slightly. Because the system is not running at full capacity, the temperature change is minimal — typically 1 to 2 degrees over time.

The fan speed in Dry Mode is usually fixed and cannot be manually adjusted. Your aircon is managing the cycle automatically to prioritise moisture removal over temperature reduction.

Dry Mode vs Cool Mode: What Is the Difference?

This is the question most people have. Both modes remove humidity. Both use the refrigerant cycle. But they behave very differently in practice.

Cool Mode

Runs the compressor and fan at full or user-set capacity. Priority is reaching and maintaining your target temperature. Humidity is reduced as a side effect of cooling. Best when it is genuinely hot outside.

Dry Mode

Runs the compressor and fan at reduced, controlled capacity. Priority is removing moisture from the air. Temperature drops only slightly. Best when the air is humid but the temperature is mild — not scorching.

Common Mistake

Using Dry Mode on a 35-degree day will not keep you comfortable. It is not designed to handle extreme heat. If the temperature is high, switch to Cool Mode and let your air conditioner do its primary job.

When Should You Use Dry Mode?

Dry Mode is most useful in specific weather conditions that Sydney and surrounding areas experience regularly. Here is when it genuinely earns its place:

• Overcast, muggy days in spring or autumn — when the temperature is comfortable but the air feels thick and sticky.
• After overnight rain — humidity levels are high in the morning but temperatures are not yet hot enough to justify full cooling.
• Coastal and humid areas — properties near the water or in high-humidity suburbs deal with persistent ambient moisture that Dry Mode handles well.
• Mould-prone rooms — laundries, bathrooms without exhaust fans, or poorly ventilated bedrooms where surface moisture accumulates.
• When you feel sticky but not hot — if your instinct is to turn on the aircon but the temperature is only 22 to 24 degrees, Dry Mode is probably the right choice before jumping straight to cooling.

✓

A Simple Rule of Thumb

If you feel hot, use Cool Mode. If you feel clammy or sticky but not particularly hot, try Dry Mode first. You may find it resolves the discomfort without the energy cost of running a full cooling cycle.

Does Dry Mode Actually Cool the Room?

Yes — but only slightly, and that is by design. Because the compressor and fan run at reduced capacity, the room temperature may drop by one or two degrees over an extended period. You will not feel a strong blast of cold air.

What you will notice is that the air feels less oppressive. Humidity is what makes warm temperatures feel unbearable. Reduce the moisture in the air and 24 degrees feels far more comfortable than it did at the same temperature with high humidity. That is the effect Dry Mode delivers.

If you need genuine temperature reduction — say you are coming home to a 30-degree house — run Cool Mode first to bring the temperature down, then switch to Dry Mode to maintain comfort once the room has cooled.

Does Dry Mode Use Less Electricity?

Generally, yes. Because the compressor and fan run at lower capacity in Dry Mode, it draws less power than running your system in full Cool Mode at a low temperature set point. For humid but mild days where you do not actually need aggressive cooling, Dry Mode can be a cost-effective alternative.

That said, Dry Mode is not a dramatic energy saver. If you leave it running all day when you do not actually need dehumidification, you are still consuming electricity. Use it purposefully — when conditions call for humidity control, not as a default substitute for cooling.

For more on how much your system costs to run day to day, check our guide on keeping your aircon running efficiently with regular servicing.

Frequently Asked Questions

What does the dry mode symbol look like on a remote?

The Dry Mode symbol is typically a water droplet or teardrop icon on your remote control. Some brands display it as a small drop with rays or alongside the word “Dry”. It is usually located near the Cool, Heat, Fan, and Auto mode buttons.

Can I leave Dry Mode running overnight?

Yes, you can run Dry Mode overnight, particularly if you live in a humid area or your bedroom tends to feel clammy. Because it runs at lower capacity than cooling mode, it is quieter and more energy-efficient for overnight use. Just ensure your room does not get too cold as the night air cools down.

Is Dry Mode the same as using a dehumidifier?

It works on the same principle — condensing moisture from the air — but a dedicated dehumidifier is generally more effective at pure moisture removal and does not cool the air at all. Dry Mode on an air conditioner is a useful hybrid: it reduces humidity while keeping the temperature roughly stable. For extreme humidity issues, a standalone dehumidifier may be more appropriate.

Why does my aircon sometimes switch out of Dry Mode automatically?

Some air conditioners have smart sensors that detect when the room temperature drops below a certain threshold and pause the compressor temporarily to prevent overcooling. This is normal behaviour in Dry Mode and is a protective feature, not a fault. The system will resume the cycle once conditions allow.

Does Dry Mode work with all types of air conditioners?

Dry Mode is available on most modern split systems, multi-head systems, and ducted air conditioners. It is not available on older units or basic window and wall units that only offer on/off cooling. Check your remote or user manual for the teardrop symbol to confirm your unit supports it.

Should I use Dry Mode or a ceiling fan to deal with humidity?

A ceiling fan does not remove humidity — it just moves air around, which can feel refreshing but does nothing about moisture levels. If the air is genuinely humid and clammy, Dry Mode will address the root cause. If you just need air movement on a mild day, a fan is sufficient and uses far less energy.

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The post What Is Dry Mode on an Air Conditioning System? appeared first on Air-Max Air Conditioning Pty Ltd.

Replacing ducted gas heating is a big decision. Done right, it can cut your energy bills, improve comfort zone by zone, and future-proof your home as gas costs continue to rise. Done poorly, you end up with a patchwork of mismatched units, walls full of abandoned vents, and a rebate quote that looked cheap until the hidden extras showed up.

This guide covers everything you need to know before you commit. From honest cost comparisons to what actually happens to your old gas vents, we’ve laid it out in plain language so you can make the right call for your home.

1. Split Systems vs Ducted Gas Heating: Which Is Better for Older Homes?

Older homes in Sydney were built for gas. The ducted heating system runs through the ceiling or under the floor, and it’s been doing its job for 20-plus years. So why switch?

Mainly because gas prices have roughly doubled in a decade, and that old heater is almost certainly far less efficient than what’s available today.

Split system air conditioners run on electricity and use a heat pump process, meaning they move heat rather than generate it. Modern units can deliver 3-4 units of heat for every 1 unit of electricity consumed. No gas heater can match that ratio.

Older homes key consideration: If your home has solid brick walls or limited roof space, a split system is often the easier installation compared to a full ducted system replacement. One outdoor unit per group of rooms, minimal structural work, and no requirement to disturb existing ceiling cavities.

2. Multi-Head Split System vs Individual Split Systems: Which Is Better?

Once you’ve decided to go with split systems, the next question is whether to run individual units in each room or connect multiple indoor heads to a single outdoor unit. Both approaches work — but they suit different homes and budgets.

A multi-head split system connects 2-5 indoor units to one outdoor compressor. Individual split systems give each room its own dedicated outdoor unit. Here’s how they compare:

Our recommendation: For a 3-4 bedroom home replacing ducted gas, a combination often works best. Install a multi-head system for the living areas (where rooms are used simultaneously) and individual units for bedrooms (where independent operation matters). Ask your installer to model both options with running cost estimates before deciding.

3. Ducted Reverse Cycle vs Split Systems: Which Is Best on a Budget?

When you’re replacing gas heating, you essentially have two paths: swap to a ducted reverse cycle system (which uses your existing ductwork) or install split systems room by room. Both cost money upfront. The right choice depends on your home’s layout, your existing ductwork condition, and what budget you’re working with.

The honest answer: if your existing ductwork is less than 10 years old and in good condition, ducted reverse cycle is worth considering seriously. If your ducts are older, leaking, or you only need 2-4 rooms covered, split systems almost always deliver better value per dollar spent. Always get a ductwork condition assessment before committing to a ducted reverse cycle quote — duct replacement costs can blow out a budget quickly.

4. What Happens to Old Gas Heating Vents After You Install Split Systems?

This is the question most homeowners don’t think to ask until after the split systems are installed. You’ve got warm rooms, lower bills — but now there are rectangular holes in your ceiling (or floor vents) that used to be connected to your ducted gas heater. What do you do with them?

The answer depends on whether you’re keeping any part of the gas system, what condition the ducts are in, and how much finish work you want to invest in.

Important: Gas appliance decommissioning and gas line capping must be carried out by a licensed gasfitter — not the air conditioning installer. Make sure your quote includes clarity on who handles this work and whether it is priced in. In NSW, capping a gas line requires a licensed plumber with a gasfitting licence. Do not leave a gas line uncapped.

5. Are Split System Rebates Worth It? What to Check Before You Say Yes

Split system rebates sound great on paper. The NSW and Federal governments have programs that can reduce the cost of upgrading to an energy-efficient reverse cycle system. In some cases, rebates and incentives can shave $600–$1,500 off the installed cost. But there are conditions, and not every rebate is as straightforward as the flyer makes it look.

The bottom line on rebates: they are real and they do reduce your cost. But treat them as a bonus on a good decision, not the reason to rush a decision. A well-specified split system at full price will still pay for itself far faster than a cheap unit chosen purely to qualify for a rebate program. Our team at Air-Max Air Conditioning installations can confirm which rebates currently apply to your specific situation before you commit.

6. Why Cheap Rebate Split System Quotes Need a Closer Look

The rise of government rebate schemes has also given rise to a particular type of quote that looks outstanding until you read the fine print. We see it regularly — homeowners call us after accepting a rebate quote, only to find out the system installed is undersized, the brand is obscure, the warranty is minimal, or there are “extras” that weren’t mentioned upfront.

Here’s what to look for when reviewing any quote that leads with a rebate or discount:

Our honest take: The cheapest rebate quote is almost never the best outcome. A correctly sized, properly installed system from a reputable brand will run for 10-15 years with minimal servicing. A cut-price job may save you $400 upfront but cost you three times that in repairs, higher running costs, and premature replacement. Get at least two quotes. If one is significantly cheaper than the other, ask exactly where the saving is coming from.

Ready to Make the Switch?

Get an honest, itemised quote from Air-Max. We’ll assess your current heating setup, confirm which rebates apply, and recommend the right system for your home, no vague pricing, no hidden extras.

Frequently Asked Questions

Is it worth replacing ducted gas heating with split systems?

In most cases, yes. Modern reverse cycle split systems are 3-4 times more efficient than gas heating on a cost-per-unit-of-heat basis, and they also provide cooling in summer. The payback period depends on your current gas usage, but most households recover the installation cost within 3-5 years through lower bills.

Can I keep my gas ducting and just replace the heater unit with a reverse-cycle system?

In some cases, yes. If your ducting is in good condition and the layout is compatible, a ducted reverse cycle system can connect to existing ductwork. However, older ducting is often leaky, undersized for reverse cycle airflow, or made from materials that degrade over time. A condition assessment is essential before committing to this path.

Do I need a licensed gasfitter to remove my old gas heater?

Yes. In NSW, decommissioning a gas appliance and capping the gas supply line must be carried out by a licensed plumber with a gasfitting licence. This is separate from the air conditioning installation work. Ensure your quote clarifies who handles this and that it is compliant.

How many split system units do I need to replace the ducted gas heating?

It depends on your home’s layout and which rooms you actually use. Most 3-4-bedroom homes use 2-4 split-system units effectively: one large unit for the main living area and individual units for regularly occupied bedrooms. You don’t need to replicate every gas vent with a split system.

Which split-system brands are most reliable?

Daikin, Mitsubishi Electric, and Fujitsu are consistently rated as the most reliable brands in Australia, with strong warranty support, widely available parts, and established service networks. Air-Max installs all three and can advise on the best option for your room sizes and budget.

The post Should You Replace Ducted Gas Heating with Split Systems? What Homeowners Need to Know appeared first on Air-Max Air Conditioning Pty Ltd.

If this sounds familiar, you’re not alone. Remote access issues with the MyAir smart controller are one of the most common complaints we hear from ducted air conditioning owners across Sydney. The good news? Most of the time, it’s fixable without a technician callout.

This guide walks you through every known cause and every fix.

In this guide, AirMax Air Conditioning explains every known cause and every fix, from simple settings you can check right now to the trickier network issues that often get overlooked, and when it is time to call a technician.

Why MyAir Works on Wi-Fi but Not Mobile Data

The short answer: MyAir was originally designed to communicate over your local home network. When you’re on Wi-Fi at home, your phone and the MyAir tablet are on the same network, so they can talk directly. When you leave home and switch to mobile data (4G or 5G), that direct local connection disappears.

Remote access over mobile data relies on the MyAir tablet being reachable via the internet, which introduces a whole different set of requirements. Here’s what has to work for remote access to succeed:

The frustrating part is that many of these issues look identical from the outside. The app just says it can’t connect; it doesn’t tell you which of the five things above is actually broken.

MyAir App Not Connecting Remotely: Common Causes and Fixes

Here are the most common causes of MyAir remote access failures, ranked from easiest to fix to most complex:

Smart Air Conditioning Not Connecting Outside the Home? Here’s What to Check

Before booking a service call or assuming it’s a software problem, run through this checklist. These are the home network and device settings that most commonly cause remote access to break — and they are almost always overlooked.

A note on mesh systems: Mesh Wi-Fi networks like TP-Link Deco, Google Nest, and Eero are generally reliable, but some models have AP isolation enabled by default. This prevents devices on the mesh from communicating with each other or with external connections. If your MyAir tablet is on a mesh node different from your router, check the Deco app settings for any isolation or firewall rules that may be blocking the connection.

MyAir App Says It Needs an Update but Everything Is Updated — What Now?

This is one of the most frustrating situations MyAir users report. The app displays an error suggesting an update is required, but when you check the App Store or Google Play, everything is already on the latest version.

Here’s what’s actually happening and what you can do:

How to Fix MyAir Remote Access Problems on iPhone and Android

The steps differ slightly between iPhone and Android. Work through these in order before calling a technician.

MyAir Remote Access Not Working After an App Update

App updates are meant to improve things. But with MyAir, an app update can sometimes break remote access that was working perfectly before.

This usually happens because the update changes how the app authenticates with the controller, and if the tablet firmware hasn’t been updated to match, the two fall out of sync.  And if your system needs a hands-on inspection, our team offers air conditioning maintenance and servicing across Sydney.

If your remote access stopped working after you updated the app, here’s what to check:

Could Your Wi-Fi or Mesh Network Be Causing the Problem?

Yes, it is possible.

One of the most overlooked causes of MyAir remote access failures is the home Wi-Fi network itself. Most people assume if the internet is working, the network is fine. But for smart home devices like the MyAir tablet, how your network is configured matters just as much as whether it is online.

Mesh systems like TP-Link Deco, Google Nest Wi-Fi, and Eero are increasingly popular in Australian homes and are generally excellent. But they introduce specific network behaviours that can silently break smart device connectivity.

When to Call a Technician for MyAir or Smart AC Control Problems

Most MyAir remote access problems can be resolved by the homeowner. But there are situations where the issue goes beyond what you can fix yourself. Air-Max provides ducted AC repairs across Sydney, including smart controller and connectivity issues.

Here’s a clear guide on when DIY troubleshooting ends and a professional technician visit is needed.

TP-Link Deco users: Open the Deco app, go to More > Advanced and check for any isolation or firewall settings. Also confirm whether your Deco is in Router Mode or Access Point Mode. If it’s in Access Point Mode with a separate ISP modem, smart device traffic can be blocked at two different points.

If you’re running Deco behind an ISP modem, make sure the Deco is set as the primary router to avoid double-NAT issues.

Still Having Trouble with Your MyAir System?

If you’ve worked through every step above and your MyAir remote access still isn’t working, it’s time to get a professional on site. Our team has been servicing ducted air conditioning systems across Sydney for over 30 years.

The post Why Does MyAir Work on Wi-Fi but Not Mobile Data? appeared first on Air-Max Air Conditioning Pty Ltd.