Air con
Can air conditioning heat my home in winter?
3 min read · Last updated · Reviewed for accuracy before publishing
Yes — and it's the half of the value most people miss. A home air-conditioning unit is an air-to-air heat pump: in winter it runs in reverse and heats the room, and because a heat pump moves heat rather than burning fuel to make it, on the datasheets for the units in our range you get roughly 4.7 to 5.2 kilowatts of heat per kilowatt of electricity (standard test conditions). For heating the rooms you actually live in — a home office, a bedroom, a snug — it's far cheaper to run than an electric radiator. It cools in summer and heats in winter from the same unit.
How it heats
The same refrigerant cycle that pulls heat out of a room in summer runs the other way in winter, pulling warmth from the outside air (there's usable heat in cold air) and delivering it inside. It's the same principle as a fridge, in reverse.
That's why an air-to-air unit delivers several times more heat energy than the electricity it uses, unlike an electric radiator that's one-for-one.
Where it makes sense
It shines for room-by-room heating: the home office you're in all day, a bedroom, an extension the central heating never quite reaches. It heats that space fast, cheaply and controllably, while your boiler carries the rest of the house. Lots of people fit it for summer cooling and are then surprised it becomes their favourite winter heater.
The efficiency, honestly
Running cost depends on the unit's SCOP rating and how hard it's working against the outside temperature, but for heating a single room it should comfortably undercut electric heating: the Mitsubishi Electric MSZ-AY25 datasheet rates 3.2 kW of heating output for 0.78 kW of electricity at nominal conditions. Against gas it is closer: at Ofgem's price cap, electricity is 26.32p per kWh and gas 7.97p, so it needs to deliver more than three units of heat per unit of electricity to match gas on running cost. It's not a whole-house central-heating replacement on its own — it's the cheap, efficient way to heat the rooms that matter most.
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.
“The same unit that rescues July quietly becomes a far cheaper heater than an electric radiator come January — several kilowatts of heat for one of electricity.”
Ask us about air-to-air heating →
Sources
- 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
- 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
- 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
- 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)
- Ofgem — Boiler Upgrade Scheme (£7,500 for air-to-water, ground and water source heat pumps; £2,500 for air-to-air heat pumps for residential properties only; installers must be MCS certified; accessed 19 Oct 2026)
- Ofgem — Boiler Upgrade Scheme: property owners (the new system must "replace an existing fossil fuel or electric heating system" and not replace an existing low-carbon one; hybrid systems such as a fossil fuel boiler plus an air source heat pump are not eligible; air-to-air heat pumps £2,500, residential properties only; £9,000 for air-to-water or ground source in eligible off-gas-grid homes from 21 Jul 2026 to 31 Mar 2027; accessed 19 Oct 2026)
Datum's engineers install and service boilers, air conditioning, heat pumps and plumbing across South Hertfordshire and London. Guides are written from real jobs, not brochures.