Air Conditioning Energy Saving Tips

Cut your power bill without losing comfort. Practical tips from 35 years on the tools.

Air Conditioning Energy Saving Tips

Most of what drives your power bill is easy to fix.

Temperature settings, filter condition, unit placement, system sizing — these four things account for the bulk of air conditioning running costs. Get them right and you're already ahead of most households. The tips below are in order of impact: the ones that save the most money come first.
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Energy Saving Tips

8 things that actually cut your bill

These are the habits and settings that make a measurable difference. Skip the ones that don't apply to your setup — focus on the ones that do.

Gloved hands applying silicone sealant with a caulking gun around a window frame to improve draught sealing

Set it to 24–26°C in summer

Every degree colder costs you roughly 10% more to run. 24°C is comfortable. 21°C is expensive. In winter, 20°C heating is the sweet spot — drop it to 18°C at night. Most people can’t feel the difference between 20 and 22, but the meter can.
Modern office reception area with exposed ceiling pipes, glass partitions, indoor plants, and a green living wall

Clean the filters every 3 months

A clogged filter makes your system work 15–25% harder for the same result. Pull the filter out, rinse it under a tap, let it dry. Takes 5 minutes. If you’re on a split system, it’s usually two clips and a slide. Ducted systems have return air grilles — same deal. Do it every school holidays and you’ll never have a problem.
Man in black cap removing the dusty filter from an open wall-mounted split system air conditioner

Only cool the rooms you’re using

If you’ve got a ducted system with zone control, turn off zones for rooms that are empty. Cooling a spare bedroom no one’s in all day is dead money. If you’ve only got one split in the living room, close the hallway door so you’re not cooling the whole house through one unit. Simple stuff.
Outdoor air conditioning condenser unit installed on a balcony floor next to sliding glass doors

Seal gaps — your AC is fighting every leak

Up to 35% of the air you’re paying to cool escapes through gaps around doors, windows, and ceilings. Weatherstrips cost $10 from any hardware store. Draught excluders on the bottom of doors help a lot. If your ceiling is poorly insulated, your system is working twice as hard — insulation alone can cut energy use by 40% in older homes.
Hand holding an air conditioner remote control showing 26 degrees Celsius with a split system unit in the background

Keep the outdoor unit out of direct sun

An outdoor unit sitting in full western afternoon sun can be 10°C hotter than one in shade. That temperature difference directly affects how hard it has to work. If yours is copping full sun, a simple shade structure above it (not blocking airflow around it) makes a real difference. Also keep the area around it clear — at least 30cm on all sides.
Man leaning back at a home office desk with hands behind his head, relaxed by an open window with green trees outside

Use the timer — or get wifi control

Set the system to turn off an hour after you go to bed and come back on 30 minutes before you get home. You sleep fine, the house is comfortable when you walk in, and you’re not cooling an empty house all day. Modern Daikin, Mitsubishi, and Fujitsu systems all have wifi controllers built in. Once you’ve got it on your phone it’s dead easy to manage.
Close-up of the SLEEP button on an air conditioning remote control

Right-sized beats high-star-rated every time

A 6-star 2.5kW split won’t cool a large open-plan living room — it’ll run flat out and still not get there. An undersized unit running at 100% costs more to run than a correctly sized unit running at 60–70%. More stars is better when the size is right. Getting the size wrong first is the most expensive mistake you can make.
Bearded tradesman in overalls and safety glasses giving a thumbs up while opening a split system indoor unit

Annual service keeps efficiency up

A system that’s low on refrigerant runs longer cycles and uses more power. Coils caked in grime transfer heat poorly. Electrical contacts that are slightly burnt cause the compressor to draw more current. None of these are things you’ll notice until your bill climbs — but a yearly service catches all of them. If your system is 5+ years old and hasn’t been serviced, it’s worth a look.
Large double-fan ducted outdoor air conditioning unit mounted against a modern timber-clad home in snowy conditions
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When to Call a Tradie

Signs your system is working too hard

What to look for and when to act

Some things you can fix yourself. Others need a licensed technician. Here’s how to tell the difference.

Clean filters, proper settings, and shading the outdoor unit are all DIY. But if the system isn’t reaching temperature even on moderate days, if it’s making noises it didn’t used to, or if you’re seeing ice on the indoor unit — those are refrigerant or mechanical issues. Don’t ignore them. A problem that costs $200 to fix now can cost $800 if left to run for another summer.

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    Not reaching temperature on mild days

    If it’s 28°C outside and the system can’t hold 24°C inside, the system is either too small, low on refrigerant, or has a coil problem.

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    Power bill jumped without obvious reason

    A sudden spike in electricity costs (not explained by usage) often means the compressor is drawing more current than it should. Get it looked at.

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    Ice forming on the indoor unit

    Turn it off immediately. Ice on the coil is almost always low refrigerant or a blocked filter causing restricted airflow. Running it further risks compressor damage.

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    Water dripping inside

    The condensate drain is blocked. Not an emergency but needs clearing. If ignored it causes mould inside the unit and eventually water damage to the wall.

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    Unusual noises — rattling, grinding, or hissing

    Rattling is usually a loose panel or fan blade. Grinding is bearings. Hissing is refrigerant. None of those fix themselves — get them diagnosed.

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    System more than 10-12 years old

    Older systems lose efficiency gradually. By year 10-12, a new 6-star system can use 30-50% less power than your existing one running at degraded capacity. The payback period is real.

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    Smell — musty or burning

    Musty smell is mould inside the indoor unit — common, fixable with a proper service clean. Burning smell is electrical. Turn it off and call someone that day.

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    Struggling on days over 38°C

    Systems have rated capacity at 35°C outdoor temp. On a 40+ degree day, output drops. If yours completely gives up, it may be undersized for worst-case days. Worth a conversation about the right size.