Can Air Conditioning Heat Your Home? Using Aircon for Heating in Winter
Can Air Conditioning Heat Your Home? Using Aircon for Heating This Winter
Most people think of air conditioning as something you only switch on during a July heatwave. But the wall-mounted split system you'd install to keep a bedroom cool in summer is also one of the most efficient ways to heat that same room when the weather turns cold.
Yes, modern air conditioning can heat your home. Almost every split system sold in the UK today is a reverse-cycle unit, which means it works as an air-to-air heat pump. In heating mode it pulls warmth from the outside air, even when it's close to freezing, and moves it indoors. For every unit of electricity it uses, it can deliver several units of heat, making it far more efficient than electric heaters and a strong option alongside, or instead of, a gas boiler in the rooms you use most.
How Air Conditioning Heating Works
In cooling mode, an air conditioner takes heat out of your room and dumps it outside. In heating mode it simply runs that process in reverse. A valve inside the outdoor unit switches the direction of the refrigerant, so it absorbs heat from the outside air and releases it through the indoor unit on your wall.
That's why air conditioning heating is so efficient. It isn't creating heat by burning fuel or glowing an element red hot. It's moving heat that already exists from one place to another. It's the same technology as an air source heat pump. The only difference is that it heats the air in the room directly, rather than heating water for radiators.
Aircon Heating vs Other Ways to Heat a Room
| Air Conditioning (Heat Mode) | Gas Boiler & Radiators | Electric Heaters | |
|---|---|---|---|
| Efficiency | Very high: several units of heat per unit of electricity | High for modern condensing boilers | One unit of heat per unit of electricity |
| Running costs | Low | Low to moderate | High |
| Heat-up speed | Fast, warms the air in minutes | Moderate | Fast in small spaces |
| Room-by-room control | Yes, each indoor unit is controlled separately | Limited without smart TRVs | Yes |
| Cooling in summer | Yes | No | No |
| Carbon emissions | Low, and falling as the grid gets greener | Higher (burns fossil fuel) | Depends on your tariff |
The Pros and Cons
Advantages
- Far more efficient than plug-in electric heaters
- One system gives you heating in winter and cooling in summer
- Warms a room quickly, with no waiting for radiators
- Heat only the rooms you're using, on their own schedule
- Takes pressure off an ageing boiler
- Many units filter and dehumidify the air too
Things to Consider
- Heats the air, not the fabric of the room, so it cools quickly when switched off
- Doesn't provide hot water, so you'll still need your boiler or cylinder
- Efficiency drops a little in very cold snaps
- Needs professional installation by an F-Gas engineer
- Portable units are much less effective at heating than wall-mounted splits
Does It Work When It's Freezing Outside?
Yes. There's still usable heat in the air even at sub-zero temperatures, and modern inverter units from brands like Panasonic, Daikin and Mitsubishi are rated to keep heating well below freezing. Efficiency does dip as it gets colder, and the outdoor unit will occasionally run a short defrost cycle to clear frost from its coil. You might notice the indoor fan pause for a few minutes while this happens. That's completely normal.
For a typical winter in Kent, Essex and South East London, where temperatures rarely stay far below freezing for long, a correctly sized split system will keep a room comfortably warm all season.
Where Aircon Heating Makes the Most Sense
Air conditioning works best as a heating source in rooms that are hard or expensive to keep warm with your existing system:
- Conservatories and orangeries that are too cold in winter and too hot in summer
- Loft conversions and extensions that weren't added to the central heating
- Garden rooms and home offices where you'd otherwise run an electric heater all day
- Main living spaces, so you can turn the boiler down and heat just the rooms you're in
- Flats and small homes without gas, where it can replace storage or panel heaters
Getting the Most From Heating Mode
Set the unit to "Heat" rather than "Auto" in winter, and pick a steady temperature, usually 20 to 21°C, rather than turning it up high and switching it off again. Heat pumps are at their most efficient when they run gently and consistently. Keep the filters clean and the outdoor unit clear of leaves and garden clutter so it can breathe. We cover more habits like these in our guide to using air conditioning efficiently.
Sizing matters too. A unit that's too small will run flat out on cold days and still struggle to keep up. If you're not sure what capacity you need, our free survey will confirm the right size for each room.
Common Questions
Is it cheaper to heat with air conditioning than gas?
It depends on your energy tariff and how efficient your boiler is, but a modern split system often costs a similar amount to gas for heating a single room, and much less than electric heaters. It's most cost-effective when you heat only the rooms you're using rather than the whole house.
Can air conditioning replace my central heating?
In smaller homes and flats, a multi-split system can heat every main room. In most larger homes it works best alongside the boiler, taking on the rooms you use most while the boiler handles hot water and the rest of the house.
Does my air conditioner have a heating mode?
If it's a wall-mounted split system installed in the last ten years or so, it almost certainly does. Look for a sun symbol or "Heat" on the remote control.
Why is my air conditioner blowing cold air in heat mode?
For the first few minutes, the indoor fan holds back until the coil is warm. It will also pause during a defrost cycle. If it keeps blowing cold air for more than 10 to 15 minutes, check it's set to Heat and that the filters are clean, then get it looked at.
Does using air conditioning for heating need extra servicing?
No extra work, but a system that runs all year round benefits from an annual service to keep it efficient. See our air conditioning servicing page for what's included.
Get a Free Survey
Our F-Gas qualified engineers install heat pump air conditioning across Dartford, Kent, Essex, Surrey and South East London. We'll look at the rooms you want to heat and cool and recommend a system that's correctly sized for them.
Find out more about our air conditioning installation service.