Air conditioning running cost calculator
Compare the running cost of split AC, air-to-air heat pumps, portable units and fans at the current Ofgem price cap or your own tariff.
System
Rooms cooled
45 days is a typical UK summer of use. A hot one can double it.
Defaults to the Ofgem price cap average for 1 October 2026 to 31 December 2026. Check your bill for yours.
Single-split air conditioning
10.8p
an hour
£39
a year, 148 kWh
A year of the same use, by system
- Single-split air conditioning£39
- Multi-split air conditioning£39
- Air-to-air heat pump£39
- Ducted air conditioning£53
- Portable air conditioning£73
- A 45 W fan (cools people, not the room)£4
Efficiency (SEER): 6.1 for split, multi-split and air-to-air, 4.5 ducted, 2.6 portable. About 1.25 kW of cooling per room averaged over an hour of use (2 kW for a portable running flat out).
How this works
Electricity used = cooling delivered divided by the system's efficiency. We assume about 1.25 kW of cooling per room averaged over an hour of use (a typical 2.5 kW room unit rarely runs flat out), and 2 kW for a portable unit, which does.
Efficiency is the seasonal energy efficiency ratio (SEER): at least 6.1 for split, multi-split and air-to-air units rated A++ for cooling, about 4.5 for ducted systems because of duct losses, and a single-point efficiency of about 2.6 for portable units. The unit rate defaults to the Ofgem price cap average for Direct Debit customers in England, Scotland and Wales, 26.32p per kWh from 1 October 2026 to 31 December 2026.
The optional council area scales your usage by the Met Office's projected cooling degree days (degrees above a 22°C daily mean, summed over the year) between the 2001 to 2020 climate and a world 2.5°C warmer than pre-industrial. These are the same numbers the Home Cooling Checker uses.
Sources
Questions people ask
How much does air conditioning cost to run per hour in the UK?
About 5.4p an hour to cool one room with a modern split unit at 26.32p per kWh. A portable unit costs about 20.2p an hour.
How do I find my electricity unit rate?
It is on your bill or in your supplier app, in pence per kWh. On a time-of-use tariff, use the rate for the hours you would run the cooling.
Why is a portable air conditioner so much more expensive to run?
It is far less efficient (about 2.6 against 6.1 for a split unit), runs flat out, and loses cooling through its window hose and gaps.