What does inverter actually mean?
Daikin compares it to a car's accelerator: the system keeps adjusting its heating or cooling output as the room temperature changes. ActronAir describes the same thing from the inside, a compressor with variable speeds that rise and fall with demand.
A fixed-speed, or non-inverter, unit works more like a light switch. ActronAir says it runs by switching the motor on or off, so it's either going full tilt or not at all.
Rinnai says every one of its current split system ranges uses inverter technology, and other brands put the word up front too. Carrier, for example, lists inverter hi wall, ducted and multi split systems.
Inverter vs non-inverter
| Inverter | Fixed speed (non-inverter) | |
|---|---|---|
| How the compressor runs | Speeds up and slows down with demand | Full speed, or off |
| Holding a temperature | Eases back once the room is close | Cycles on and off around the setting |
| Against its rated figures | CHOICE says real running costs may be lower than rated | Draws full power whenever the compressor runs |
| Where you'll find it | Across new splits, multi-heads and ducted systems | Mostly in older systems |
Why an inverter can use less than its label suggests
Rated figures assume the unit is working hard. The federal Energy Rating calculator notes that air conditioners may run below their rated capacity, so the real cost for the hours you pick may be lower than it shows. CHOICE makes the same point about modern inverter splits.
To estimate your own, use the input power (what the unit draws), not the capacity (what it delivers). Mitsubishi Electric lists both in kW, which makes them easy to mix up. RAA's method is input power in kW, times your rate per kWh, times the hours you run it. Our running cost tool does that sum with your own power rate.
An inverter won't fix the wrong size
Inverters cope with a range of loads, but they don't rescue a unit that's too big or too small. Rinnai says an oversized system short cycles, switching on and off too often, dehumidifies poorly and wears faster. An undersized one struggles to heat or cool, uses more energy and has a shorter life.
Hot days matter too. ActronAir says above 35 degrees an air conditioner loses cooling capacity, giving the example of a 14 kW system dropping to 10 kW or 12 kW. Mitsubishi Electric calls a professional heat load calculation essential, and our sizing guide explains what goes into one.
Questions worth asking instead
- Is this model an inverter? It'll say on the spec sheet.
- What's the rated input power in heating and in cooling?
- How did you size it for this room?
- How many stars does it have for our climate zone?
- I'm replacing an old fixed-speed unit. Are you sizing the new one fresh, or copying the old kW?
What you can do, and what needs a licence
You can
- Use the setback or sleep mode if yours has one. Mitsubishi Electric's i-save example holds the room 2 to 3 degrees warmer in cooling, or cooler in heating, while you sleep or are out.
- Keep the filters clean. Daikin says swapping a blocked filter for a clean one can cut energy use by 5% to 15%.
- Choose a sensible setting rather than the coldest or hottest the remote allows.
- Check your model number in the manual or on the spec sheet to see whether it's an inverter.
Leave to a licensed installer
- Sizing from a heat load.
- Diagnosing a compressor or inverter board fault.
- Refrigerant work, which needs an ARC licence.
- Electrical work, and replacing an old unit.
What we'd do
Our take
Don't let the word inverter on the box sway you, because nearly everything carries it now. Put your attention on two things: the right size for the room, and the star rating for your climate zone. If you're replacing an old fixed-speed unit, ask the installer to size the new one from scratch, since the old unit's kW may never have been right.
