Portable air conditioner running costs and energy efficiency

Running cost equals power in kilowatts, multiplied by hours used, multiplied by your price per kWh. For a 1 kW unit running for eight hours at 26.32p that is 1 × 8 × 0.2632 = £2.11. Real figures are usually lower because the compressor switches off once the room reaches the target temperature.

The Ofgem price cap for 1 October to 31 December 2026 averages 26.32p per kWh for electricity on a standard variable tariff paid by Direct Debit, plus a 54.83p daily standing charge that you pay whether or not you use the air conditioner. The government has removed VAT from electricity bills until 31 March 2027.

A 7,000 BTU unit sits near the top of the first row, a 9,000 BTU unit near 1 kW, and a 12,000 BTU unit at or above 1.25 kW. Your unit's rating plate gives the exact wattage.

UK energy labelling rules classify single- and double-duct (portable) air conditioners from A+++ down to G using their energy efficiency ratio, or EER: the cooling the unit delivers divided by the electricity it uses. The thresholds are set out in the retained version of Regulation 626/2011.

In our catalogue, 35 of the 37 portable models with a listed class are rated A, so the letter alone rarely separates them. Compare the wattage and the stated cooling capacity instead. A 2.6 kW (9,000 BTU) unit drawing 1.0 kW has an EER of 2.6; one drawing 0.85 kW has an EER of about 3.0.

1. Set it to 24 to 26°C and add a fan. Moving air feels cooler, so you can raise the target and cut compressor time.
2. Block the sun first. Close curtains or blinds on sunny windows before the room heats up. Cooling air that sun is warming is the most expensive cooling there is.
3. Seal the window kit. Gaps around the hose and panel let hot air back in. Use the foam strips that come with the kit.
4. Close the door. Cool one room, not the whole house.
5. Use the timer and sleep mode. Pre-cool the room before you need it, then let the unit ease off overnight.
6. Keep the filter clean. A clogged filter chokes airflow and makes the compressor work harder. Rinse it every two weeks in use.
7. Size it properly. A unit that is too small runs flat out; one that is too large cycles on and off. Use the BTU calculator.
8. Reduce internal heat. Turn off unused electronics and avoid the oven in the hottest part of the day.

If running cost is your top priority and you can have it fitted, a split system is cheaper to run. If you rent or cannot fix anything to the wall, a portable unit is the practical choice. Our what is a portable air conditioner guide compares all four options.

Ofgem resets the price cap every three months and the next change applies from 1 January 2027. The VAT relief on electricity is scheduled to end on 31 March 2027. Your own tariff, whether fixed, variable or time-of-use, may also differ from the cap. Put your real rate into the running cost calculator rather than relying on the average above.