Can an air conditioner heat a room as well as cool it?

Yes — any air conditioner marked 'heat pump' or 'reverse cycle' can run its refrigerant cycle backwards to heat. It moves heat from the outdoor air into the room rather than generating heat directly, which is why it can deliver 3–4 kW of heat for every 1 kW of electricity.

What is COP and SCOP for a heat pump?

COP (Coefficient of Performance) is heat output divided by electricity input at one condition; SCOP is the seasonal average. A COP of 3.5 means 3.5 kW of heat per 1 kW of power. Higher is cheaper to run — it's the heating equivalent of EER/SEER for cooling.

Is heating with an air conditioner cheaper than electric heaters?

Almost always. A plug-in electric heater is 100% efficient (COP 1) — 1 kW in, 1 kW of heat out. A reverse-cycle heat pump at COP 3.5 delivers 3.5x the heat for the same electricity, so it costs roughly a third as much to produce the same warmth.

How do I work out the heating cost per hour?

Cost per hour ≈ electrical power drawn (kW) × your electricity rate. For a given amount of heat, divide the heat output by the COP to get the power drawn. A unit delivering 3 kW of heat at COP 3 draws 1 kW — about 24.5p/hour on a UK 24.5p/kWh tariff.

Can an Air Conditioner Heat Your Home? Heat-Pump Running Costs Explained

Published: May 24, 2026

Look at the comparison and you’ll see a heat pump badge on many units. That badge matters: a reverse-cycle air conditioner doesn’t just cool in summer — it’s one of the cheapest ways to heat a room in winter. Here’s the how and the numbers.

Heating is just cooling in reverse

An air conditioner moves heat; it doesn’t make it. In cooling mode it pumps heat out of the room. A reverse-cycle (heat-pump) unit flips a valve and pumps heat in — extracting warmth from the outdoor air (yes, even cold air contains heat) and delivering it inside.

Because it’s moving heat rather than generating it, it can deliver far more heat energy than the electricity it consumes.

COP and SCOP: the heating efficiency numbers

For cooling we use EER/SEER. For heating, the equivalent is COP (Coefficient of Performance) and its seasonal average SCOP:

COP = heat delivered (kW) ÷ electricity used (kW)

A COP of 3.5 means the unit produces 3.5 kW of heat for every 1 kW of electricity it draws. Modern inverter heat pumps typically run COP 3–4.5, dropping somewhat on the coldest days.

Why that beats a plain electric heater — and often gas

Heat source	Efficiency / COP	Cost to deliver 3 kW of heat (UK 24.5p/kWh / gas 6.5p/kWh)
Plug-in electric heater	1.0	3 kW × 24.5p = ~74p/hr
Heat pump (COP 3.5)	3.5	0.86 kW × 24.5p = ~21p/hr
Gas boiler (~90%)	0.9	3.33 kW × 6.5p = ~22p/hr

A reverse-cycle AC running at COP 3.5 costs about a third of a plug-in electric heater for the same warmth, and lands roughly level with mains gas at typical UK prices — without a gas connection or flue.

Working out heating cost per hour

The same logic as our cost-per-hour cooling metric, with COP in place of EER:

Power drawn (kW) = heat output (kW) ÷ COP
Cost per hour    = power drawn × your electricity rate

Want 3 kW of heat from a COP-3 unit? It draws 1 kW → about 24.5p/hour in the UK, 16¢/hour in the US. Try our BTU calculator to size the unit, then check the heat-pump units in the comparison.

What to watch

COP falls as it gets colder. Performance at 7°C looks great; at −5°C it’s lower. SCOP is the more honest seasonal figure.
A heat-pump AC heats the room it’s in, not your whole house like central heating. It shines for a home office, lounge or extension.
Look for the heat-pump badge in the comparison — those units do double duty, cooling in summer and heating cheaply in winter.

The bottom line

If a unit carries the heat-pump badge, its running cost isn’t just a summer number. At a COP of 3–4 it’s among the cheapest electric heating you can buy — which is why “what does it cost to run?” is the question worth asking in winter too.

Next: How much does it cost to run an air conditioner? · SEER vs EER explained · air conditioners ranked by cost to run.