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

TDThe Datum team · Heating, cooling & plumbing engineers
3 min read · Reviewed for accuracy before publishing

Cooling a typical bedroom or living room costs roughly 15–40p per hour at current electricity prices, depending on the unit size, the temperature outside and how hard it's working. Used sensibly (cooling the room you're in, doors closed, a realistic set-point), a UK summer's cooling usually totals tens of pounds, not hundreds. In winter the same unit heats the room at roughly a third of the cost of electric radiators, because heat pumps move heat rather than generate it.

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.

The winter flip-side

An air-to-air heat pump typically delivers three-plus kilowatts of heat per kilowatt of electricity. For heating one room — a home office, a bedroom — it's usually the cheapest option available, and it's why these systems make sense year-round in the UK.

Honest sizing saves money twice

An undersized unit runs flat-out and struggles; an oversized one short-cycles inefficiently. Correct sizing at the survey is the single biggest 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

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Sources & verification

TD
The Datum team · Heating, cooling & plumbing engineers

Datum's engineers install and service boilers, air conditioning, heat pumps and plumbing across South Hertfordshire and North London. Guides are written from real jobs, not brochures.

Related questions

Is air conditioning expensive to run overnight?

On sleep mode at a sensible set-point, a bedroom typically costs pence per night to keep comfortable — modern inverter units sip power once the room is at temperature.

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 — clogged filters make the unit work harder for less output. A clean-and-check keeps efficiency at spec; we recommend it annually.

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 that the filters aren't clogged — a blocked filter alone can stop it cooling. If it's still warm after that, it's usually lost refrigerant through a slow leak, which by law needs an F-Gas engineer to find and recharge — not a top-up from a bottle. We trace the leak rather than just refill it.

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