How much does it cost to run an air conditioner?
Portable AC running costs depend on the unit's power draw, how long you run it, and your electricity rate. Use the calculator below — it uses the current UK price cap rate by default.
UK Oct 2026 price cap: 24.5p/kWh
- Per day5.4 kWh
- £1.32
- Per month30 days
- £39.69
- Per summer90 days
- £119.07
How running costs are calculated
The formula is simple: (watts × hours) ÷ 1,000 = kWh per day, then multiply by your electricity rate. A 9,000 BTU portable AC drawing 900W, run for 6 hours at 24.5p/kWh, costs roughly £1.32/day or £39.60/month.
Why portable ACs cost more than you think
A portable air conditioner's compressor cycles on and off, so actual power draw varies. The rated wattage is the maximum — real-world usage is typically 60-80% of that. The numbers above are worst-case estimates. Using a timer, closing curtains, and sealing window gaps can cut your real cost by 30-40%.
Fan vs portable AC — the real difference
A pedestal fan draws about 40W — roughly £1.76/month for 6 hours daily use. A portable AC at 900W costs about £39.60/month for the same usage. That's 22× more. Fans don't actually cool the air — they just move it — but for UK nights where the temperature drops below 20°C, a fan in the window is often enough.
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