How much does a portable air conditioner cost per hour in the UK?

Heating By Ellen HartwellPublished 27 September 2026

What a portable air conditioner actually draws

UK portable units run from about 700 watts for a small bedroom machine to 2,500 watts for the largest units sold for conservatories, with most domestic models landing between 1,000 and 1,200 watts. That wide band is why a single answer to the per hour question is impossible without the plate on the back of your own machine.

De'Longhi publishes a useful anchor. The Pinguino PAC EL98 Eco is rated at 930 watts of input power for 2.7 kilowatts of cooling, and carries an A energy class. That ratio is the thing to understand. An air conditioner does not turn electricity into cold, it moves heat from inside the room to outside through a refrigeration circuit, and a good one moves about three kilowatts of heat for every kilowatt it draws.

The rating on the box is usually given in BTU rather than watts, and the two numbers describe different things. A 10,000 BTU unit is describing how much heat it can shift, not how much electricity it needs to do it. For cost you want the input power in watts, which sits on the rating plate next to the voltage.

The cost per hour and per night

At 1,100 watts an hour costs 28.7p at the Ofgem cap rate of 26.11p per kilowatt hour. A small 700 watt unit costs 18.3p an hour, the De'Longhi at 930 watts costs 24.3p, and a 2,500 watt machine costs 65.3p.

An eight hour night at 1,100 watts uses 8.8 kilowatt hours and costs £2.30. Every night for a month is 267 kilowatt hours and £69.70, which is the figure that makes people reach for the manual. A more realistic British summer, a fortnight of genuinely hot nights, comes to about £32.

Readers in the United States, where these machines run for whole seasons rather than fortnights, can use the EIA residential average of 18.34 cents per kilowatt hour. That puts the hour at about 20 cents, the night at $1.61 and a full month of nightly running at $48.95. In California, at 34.74 cents, the same month reaches $92.

Rates: Ofgem cap 1 July to 30 September 2026 at 26.11p per kWh (source), EIA residential average June 2026 at 18.34 cents per kWh (source). Checked 2026-09-22.

The single hose problem

Most portable units sold in Britain have one hose going out of the window, and that design has a flaw nobody mentions on the box.

The machine pulls air from the room, passes it over the hot condenser coil and pushes it out of the hose. That air has to be replaced, and it is replaced by outside air dragged in through every gap around the window kit, the door and the floorboards. On a hot day you are pumping warm outside air into the room you are trying to cool, which means the compressor runs longer to reach the same temperature and you pay for the extra hours.

A double hose unit takes its condenser air from outside and returns it outside, so the room is not put under negative pressure. They cost more and are harder to find, and in a room you actually need to cool they will usually get there faster on fewer kilowatt hours.

Against the alternatives

A pedestal or tower fan draws around 50 watts, rising to 100 watts for a large pedestal model, so 1.3p an hour against 28.7p for the air conditioner. The fan does not lower the air temperature at all, it moves air across your skin so that sweat evaporates faster and you feel cooler. For a lot of British nights that is enough, and it is twenty two times cheaper.

A dehumidifier at 151 watts costs 3.9p an hour. It will not cool the room either, and the compressor dumps its waste heat back into the space, so the temperature rises slightly. What it does is take the stickiness out of humid air, which for some people is the part that stops them sleeping.

Set against heating, the air conditioner looks cheap. A 2kW oil filled radiator costs 52.2p an hour, nearly double, which is a reminder that cooling a British house is a much smaller annual bill than heating one however bad a hot week feels.

Six ways to cut what it costs

• Switch to fan only once the room has come down to temperature, because the compressor is the expensive part and the fan is not.
• Seal the window kit properly with foam or tape. Every gap is warm outside air being pulled back into the room you just paid to cool.
• Set the thermostat to 24 degrees rather than 18. The machine works until it reaches the target, so a lower target simply means more compressor hours.
• Close the curtains on the sunny side of the house in the morning, since keeping heat out costs nothing and removing it costs 28.7p an hour.
• Cool one bedroom with the door shut rather than trying to cool a landing and three rooms off it, as the unit is sized for a single room and will never reach target in a larger space.
• Use the timer to run it for the hour before bed and switch to fan overnight, which is usually the difference between £2.30 and about 50p a night.

Is it worth buying one

For a top floor flat that holds heat until three in the morning, a portable unit is the only plug in device that genuinely fixes the problem, and £32 across a hot fortnight buys a lot of sleep.

For most British houses, the honest answer is that a £30 fan and a pair of blackout curtains solve eight nights out of ten for a twentieth of the running cost. Try that combination for one summer before you spend £400 on a machine that then lives in the loft for eleven months of the year.