What does air conditioning really cost to run in a UK home?

The single most common question we get asked on surveys in Camberley is simple: what will it cost me to run? The honest answer is far less than most people expect, and it is easy to work out.

A typical 2.5kW wall-mounted unit cooling a bedroom draws around 0.6kW once it has pulled the room down to temperature. At current electricity prices that is roughly 15-18p an hour of steady running. Overnight in a heatwave you are looking at well under £1.50 for a full night of comfortable sleep.

The reason is inverter technology. Older fixed-speed units switched fully on and fully off, spiking consumption every cycle. A modern inverter compressor ramps down to a trickle once the setpoint is reached, holding the room steady on a fraction of the power.

It gets better in winter. Run the same unit in heating mode and it behaves as an air source heat pump, typically returning three to four kilowatts of heat for every kilowatt of electricity. That is a coefficient of performance no gas boiler can match.

Three things make the biggest difference to your bill: correct sizing, sensible setpoints and clean filters. An oversized unit short-cycles and wastes energy. Setting 21°C instead of 18°C in cooling can halve consumption. And a blocked filter can add 25% to running costs on its own, which is exactly why we push annual servicing so hard.