How much does air conditioning cost to run per hour in the UK?
The question we get asked more than any other: 'what will it cost me to run?'. People imagine American-style bills. The reality in a UK home is pennies per hour. Here are the actual numbers, based on 27p/kWh electricity and the systems we fit every week.
Cost per hour by room size
| Unit size | Typical room | Power draw when running | Cost per hour |
|---|---|---|---|
| 2.0 kW / 7,000 BTU | Box bedroom / nursery | 0.25 – 0.4 kWh | 7p – 11p |
| 2.5 kW / 9,000 BTU | Double bedroom | 0.3 – 0.5 kWh | 8p – 13p |
| 3.5 kW / 12,000 BTU | Large bedroom / home office | 0.45 – 0.7 kWh | 12p – 19p |
| 5.0 kW / 18,000 BTU | Lounge / open-plan | 0.6 – 1.1 kWh | 16p – 30p |
| 7.1 kW / 24,000 BTU | Conservatory / large lounge | 0.9 – 1.6 kWh | 24p – 43p |
Crucially, an inverter unit does not draw full power all the time. It pulls hard for the first 20–30 minutes to get the room down, then throttles back to a trickle to hold temperature. Averaged over an evening, most bedroom units land at the lower end of these ranges.
What a typical night actually costs
A 2.5 kW bedroom unit holding 21°C overnight uses roughly 3–5 kWh over ten hours. That's 80p to £1.35 a night. Run it every night through a two-week UK heatwave and you're looking at £11–£19 on your bill — for guaranteed sleep.
A lounge unit used for four hours each evening across a hot month costs around £8–£15.
Heating mode is where it gets interesting
Air conditioning is a heat pump. In heating mode it delivers roughly 3–4 kW of heat per 1 kW of electricity. That makes it cheaper per unit of heat than a gas boiler in shoulder months — many of our customers use the AC to take the chill off in spring and autumn instead of firing the whole central heating system for one room.
Six ways to halve your running cost
- Set 22–24°C, not 18°C — every degree lower adds roughly 8% to the bill
- Use eco / quiet mode overnight rather than max fan
- Close curtains or blinds on the sunny side during the day
- Let the unit run steadily rather than blasting it on and off
- Clean the filters every 6–8 weeks in summer — clogged filters cost you 10–15%
- Pair it with solar if you have panels; peak cooling demand matches peak generation almost perfectly
How this compares to the alternatives
| Option | Cost per hour | Actually cools the room? |
|---|---|---|
| Fixed inverter AC (2.5 kW) | 8p – 13p | Yes |
| Portable AC unit | 20p – 35p | Partly — hose loses efficiency |
| Tower fan | 1p – 2p | No — just moves warm air |
| Losing a night's sleep | — | No |
FAQ
Is air conditioning expensive to run in the UK?
No. A bedroom unit costs roughly 8–13p an hour and under £1.35 for a full night. UK cooling seasons are short, so most homes spend £30–£70 a year in total.
Does air conditioning use more electricity than a fan?
Yes, around 8–10x a tower fan — but a fan doesn't lower the room temperature at all. Per degree of actual cooling, AC is far more efficient.
Will it push my home into a higher energy bill bracket?
Unlikely. Typical West Midlands households we install for see summer bills rise by £10–£25 a month during hot spells only.
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