Most people who have air conditioning use it in summer and switch it off in October. This is leaving money and comfort on the table. Modern inverter air conditioning systems are highly efficient heat pumps in winter — here is how to use the heating function effectively and what it costs.
Does Air Conditioning Work as a Heater?
Yes — effectively and efficiently. Modern inverter air conditioning systems work as heat pumps in reverse in heating mode. Rather than generating heat (like a gas boiler or electric heater), they move heat from outside air into your room. This process works down to outdoor temperatures of approximately -15°C on modern units, though efficiency reduces as temperatures drop.
At typical UK winter temperatures (0-10°C outdoors), a modern unit delivers 3-4 units of heat energy for every unit of electricity consumed. This is what engineers call a COP (Coefficient of Performance) of 3-4. Compare this to an electric panel heater at COP 1.0 (100% efficient, exactly one unit of heat per unit of electricity) or a gas boiler at approximately 0.9 (90% efficient, 0.9 units of heat per unit of gas energy).
Running Costs — Air Con Heating vs Alternatives
At 2026 UK energy prices (approximately 24p/kWh electricity, 6p/kWh gas):
- Air conditioning heat pump (COP 3.0): approximately 8p per kWh of heat delivered
- Gas boiler (90% efficient): approximately 6.7p per kWh of heat delivered
- Electric panel heater: approximately 24p per kWh of heat delivered
- Electric storage heater (Economy 7 off-peak): approximately 8-10p per kWh of heat delivered
The conclusion: air conditioning heating is roughly comparable to gas for running cost, and approximately 3x cheaper than standard electric heating. For rooms that are currently heated with electric panel heaters — particularly home offices, bedrooms and garden offices — switching to air conditioning heating delivers significant savings.
Which Rooms Work Best for Winter Heating
Home offices: The most common winter use case we see. A home office that is not on the main central heating circuit, or where the central heating takes too long to warm up in the morning, is ideal for air conditioning heating. Fast response — the room reaches temperature in 10-15 minutes — combined with good efficiency makes it the perfect supplementary heating solution.
Bedrooms: Many people prefer sleeping with central heating off or at low temperature and using air conditioning on a timer to warm the bedroom before getting up and to maintain a comfortable overnight temperature (typically 17-19°C for good sleep quality).
Garden offices and outbuildings: Spaces not connected to the main central heating system. Air conditioning is typically the most efficient heating option for a detached garden room.
Living rooms: Less compelling if already well-served by central heating, but useful for top-up heating during shoulder seasons when the central heating is not yet running.
How to Use Heat Pump Mode
Switch the remote to heating mode (sun or flame symbol). Set the target temperature — 20-22°C is typical. The unit will run the fan at low speed initially and increase output as the system warms up. Unlike a gas boiler, air conditioning heating is most efficient when set to a moderate target temperature and left to run — switching it on and off repeatedly for short periods is less efficient than running it steadily at a sensible temperature.
A Note on Defrost Cycles
In heating mode on cold days (below approximately 5°C outdoor temperature), the outdoor unit periodically enters a defrost cycle — ice that forms on the outdoor unit’s coil is melted off. During defrost (typically 2-5 minutes), the unit temporarily stops heating. This is completely normal and does not indicate a fault. You may see steam rising from the outdoor unit during defrost — this is condensate evaporating as the coil warms up, not smoke.
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