# How much does air conditioning cost to run in the UK?

*The Datum team · Heating, cooling & plumbing engineers · Datum · updated 2026-10-19 · Air con*

At Ofgem's 26.32p per kWh price cap, a typical split unit costs roughly 15–20p an hour at rated power: the Mitsubishi Electric MSZ-AY25 datasheet lists 0.6 kW cooling input, the Daikin FTXM35A 0.76 kW. A hundred hours of cooling costs about £16–£20. In winter the same unit delivers several times more heat than the electricity it uses (datasheet SCOP 4.8–5.2 for those two units).

## What drives the cost

Three things: the unit's efficiency rating (look at SEER for cooling, SCOP for heating), the gap between outside temperature and your set-point, and habits — cooling an empty house or fighting an open window is where money disappears. Daikin also recommends cleaning the filters every 2 weeks.

## The winter flip-side

An air-to-air heat pump delivers several kilowatts of heat per kilowatt of electricity: datasheet SCOP is 4.7 to 5.2 for the Mitsubishi Electric and Daikin units in our range, against one-for-one for an electric radiator. For heating one room — a home office, a bedroom — that makes it far cheaper to run than an electric radiator, and it's why these systems make sense year-round in the UK.

On the manufacturer datasheets for the Daikin and Mitsubishi Electric units in our range, rated seasonal heating efficiency (SCOP) is 4.7 to 5.2 and the quietest indoor sound level is 18–19 dB(A) — standard rating conditions, not a guarantee for your room.

## Honest sizing saves money twice

BestBuilders says an undersized unit runs flat out and never cools the room, while an oversized one short-cycles and wastes money. Correct sizing at the survey is a major running-cost decision — and it's why we size to the room, not the invoice.

> Cooling the room you are in costs pence an hour. Cooling an empty house with a window open is where the horror-story bills come from.
>
> — The Datum team, Heating, cooling & plumbing engineers

## Related questions

### Is air conditioning expensive to run overnight?

The 15–20p an hour figure above is for rated power, so treat it as a guide rather than a promise: real overnight use depends on the room, the set-point and the unit. We can talk through the numbers for your bedroom at the survey.

### Cooling or a fan — which is cheaper?

A fan is cheaper to run but doesn't cool the air, it moves it. On genuinely hot nights a right-sized AC unit at a modest set-point costs a little more and actually works.

### Does servicing affect running costs?

Yes — Daikin's manual says operating with dirty filters gives poor heating and cooling, and it recommends cleaning them every two weeks and maintenance at least once a year. A clean-and-check keeps the unit at spec.

### My air conditioning is on but blowing warm air — what's wrong?

Start with the safe checks: make sure it's in cool mode (not heat or fan-only) with the set-point below room temperature, and run through Daikin's checklist — filters not dirty, inlets and outlets unblocked, doors and windows closed. If it's still warm after that, it needs an engineer: a refrigerant leak is one possible cause, and GOV.UK says you must have F-gas qualifications to work on it. We trace the cause rather than just refill it.

## Sources & verification

- [Daikin Perfera FTXM35A datasheet figures (SCOP 5.2, quietest indoor sound 19 dB(A), nominal cooling input 0.76 kW) — via ClimaMarket, verified 9 Jul 2026](https://www.climamarket.eu/en/wall-split-ac-daikin-perfera-35)
- [Mitsubishi Electric MSZ-AY25 datasheet figures (SCOP 4.8, silent mode 18 dB(A), nominal cooling input 0.6 kW; rated heating capacity 3.20 kW at nominal heating consumption 0.78 kW) — via ClimaMarket, verified 9 Jul 2026](https://www.climamarket.eu/en/mitsubishi-electric-msz-ay25)
- [Mitsubishi Electric MSZ-AY35 datasheet figures (SCOP 4.7, minimum indoor sound level 18 dB(A)) — via ClimaMarket, verified 9 Jul 2026 and re-checked 19 Oct 2026](https://www.climamarket.eu/en/mitsubishi-electric-msz-ay35)
- [Ofgem — Energy price cap unit rates (average unit rates by Direct Debit, Great Britain, 1 Oct–31 Dec 2026: 26.32p per kWh electricity and 7.97p per kWh gas; accessed 19 Oct 2026)](https://www.ofgem.gov.uk/your-energy-supply/your-energy-bill/energy-price-cap-unit-rates-and-standing-charges)
- [BestBuilders — Air conditioning cost UK 2026 (single-room split £1,500–£3,000; Daikin or Mitsubishi single-room unit plus install £1,800–£3,200; brand choice can move a single-room price by £400–£800; two-room multi-split £2,800–£4,500; three-to-four-room £3,500–£7,000; pipe runs over about 5 m add £150–£400; budget £70–£150 a year for a service; an undersized unit "runs flat out and never cools the room" while an oversized one "short-cycles and wastes money"; accessed 19 Oct 2026)](https://bestbuilders.co.uk/costs/air-conditioning-cost-uk)
- [Daikin UK — The air conditioner does not cool or warm the room (check the air filters are not dirty, the indoor and outdoor inlets and outlets are not blocked, the temperature setting is appropriate, doors and windows are closed, airflow settings are appropriate; then contact an installer; accessed 19 Oct 2026)](https://www.daikin.co.uk/en_gb/faq/the-air-conditioner-does-not-cool-or-warm-the-room.html)
- [Daikin UK — FTXM-N / CTXM-N operation manual (the refrigerant "normally does NOT leak" and must not be vented to the atmosphere; do not repair the unit yourself; operating with dirty filters gives poor heating and cooling; cleaning the air filters every 2 weeks is recommended; maintenance at least once a year is recommended; accessed 19 Oct 2026)](https://www.daikin.co.uk/content/dam/document-library/operation-manuals/ac/split/FTXM-N,CTXM-N_3PEN485919-8S_Operation%20manual_English.pdf)
- [GOV.UK — Qualifications required to work on equipment containing F gas (for air conditioning and heat pump systems you must have qualifications to install, service and maintain, and check for leaks; "It is against the law to work with F gas if you do not have the correct qualifications"; accessed 19 Oct 2026)](https://www.gov.uk/qualifications-required-to-work-on-equipment-containing-f-gas)

---
Canonical page: https://www.datumclimate.co.uk/guides/air-conditioning-running-costs