Is Home Air Conditioning Expensive to Run?

Why running cost is not fixed

A modern inverter air conditioning system does not draw a constant amount of electricity. It works hardest when it first pulls a warm room down to temperature, then throttles back and uses considerably less power to hold that temperature.

That means the honest answer to 'what will it cost to run' is: it depends on how much heat has to be removed, how long the system runs, and what you pay per unit of electricity.

The factors that actually matter

Some of these you control day to day, and some are fixed by the building.

• Set temperature: a smaller difference between outdoor and indoor temperature means less work
• Run time: two hours before bed costs far less than all-day operation
• Room heat gain: glazing, orientation and shading are the biggest drivers
• Insulation and air tightness
• Correct sizing: an oversized or undersized system both run inefficiently
• Your electricity tariff, including any time-of-use rates

Running in heating mode

In heating mode the system works as an air-to-air heat pump, moving heat from outside into the room rather than generating it with an element. That is why heat pumps can deliver several units of heat for each unit of electricity used, with efficiency varying by outdoor temperature and the model fitted.

For heating one room quickly, many households find this useful alongside their existing central heating. We avoid quoting savings percentages, because the honest comparison depends on your gas price, electricity price, insulation and how you use the room.

Practical ways to keep running costs down

Reducing the heat that reaches the room in the first place is the most effective step, and it costs nothing to close blinds on a south-facing window during the day.

• Use blinds or external shading during the hottest part of the day
• Set a sensible temperature rather than the lowest available
• Use timers so the room is cooled before it becomes uncomfortable
• Keep doors closed so the system is not trying to cool the whole house
• Keep filters clean; a blocked filter reduces airflow and efficiency

Reading efficiency figures

Manufacturers publish SEER (seasonal cooling efficiency) and SCOP (seasonal heating efficiency) figures, along with energy labels. These are measured under standard conditions and are useful for comparing models like for like, but they are not a prediction of your bill.

We will share the published figures for the specific models we recommend so you can compare them yourself.