Think air con is just for summer? Think again – it could be key to reducing your heating bills over the winter

It might seem like utter madness to be talking about air conditioning at a time when the temperatures are dropping and homeowners are starting to think about putting the heating back on.

But while more and more people are finding air conditioning worth it in the summer, many don't realise that it can also be used to keep your home warm in the winter too.

I spoke to multiple air con experts to find out how these units can offer much more than cooling (therefore making them useful all year-round) and how they can help reduce your heating bills over the winter too.

Can you only use fitted air conditioning in the summer?

It's a common misconception that air conditioning is only useful during a summer heatwave, where homes overheat beyond the point of comfort.

While it's true that older air conditioning systems may be set up to only offer cooling, many modern versions can be used to both cool your home in summer and heat your home in winter.

'Not all fitted air conditioners are capable of heating – it’s worthwhile looking out for models labelled as ‘cooling and heating’,' explains Katie Lilywhite, air treatment expert at AO.com. 'These dual function models can be a little bit more costly, but it’s a worthy addition to your home.'

For many, this added functionality makes a fitted air conditioning system a much more worthwhile investment, given that it has a useful purpose well beyond a short-term heatwave at the height of the summer.

Can using air conditioning for heating reduce your heating bills?

A huge benefit of using air conditioning in the winter is that it can help you keep your energy bills as low as possible.

A key way to save energy at home and reduce your heating bills is to heat the room you are in rather than the whole property. This is where fitted air conditioning can come into it's own, especially if you have it installed in the room or rooms you use the most often, like a living room or home office.

'AC systems can also use zoning technology to ensure that only the spaces people are actively using are heated, which limits energy waste in unused rooms and reduces the workload of the AC,' explains Fernando de la Cruz Quintanilla, EMEA New Markets Director at Airzone. 'Modern AC systems can even use sensors that monitor when rooms are occupied, and use the data to heat accordingly and ultimately save on energy bills.'

In order for this to be most effective, you will need to keep the doors and windows to the room closed, and deal with any draughts that could see the heat you do generate go straight out the window. Literally!

Is AC more cost-effective than central heating?

Using fitted AC in heating mode can be cheaper than using your central heating, but best way to determine that is to compare the coefficient of performance (COP) which shows how much heat output you get compared to how much electricity it uses.

Nicholas Auckland, heating and energy expert at Trade Radiators, shared some calculations to help determine which is the more cost-effective heating option.

The following calculations use the upcoming October 2025 energy price cap costs of 26.35p/kWh for electricity and 6.29p/kWh for gas.

'COP stands for coefficient of performance. It shows how many times more heat you get out compared to the electricity that it uses, so the higher the COP, the cheaper the unit is to run,' explains Nicholas. 'So for example, COP 1 = £1 of electricity for £1 of heat, COP 3 = £1 of electricity for £3 of heat.

'So, heating one room with air con that needs 3kW of heat in order to stay warm (roughly an average-sized living/bedroom):

• If the AC unit runs at COP 3, then it would cost 26.35p per hour, which works out at £1.32 over 5 hours.
• If the AC unit runs at COP 4, then it would cost 20p per hour, which works out at £1 over 5 hours.
• If the AC unit runs at COP 5, then it would cost around 16p per hour, which would work out at 79p over 5 hours.

'On the other hand, heating a whole home with central heating that needs 10kW of heat in order to stay warm:

• Assuming the gas boiler is 90% efficient, it would cost 7p per kWh of heat. This would cost 70p per hour, and £3.50 in 5 hours.

So using air conditioning to heat the specific room you are in would be cheaper than using your central heating. However, if you had air conditioning in multiple rooms and used them all to provide heating, then that would cost more than using your central heating.

While air con in heating mode in a single room might be a more cost-effective option, you need to consider how your home is used. If you have a busy family home with people moving between different rooms all the time, then relying on fitted air con in one room probably isn't going to cut it, and heating the whole house with your central heating is the best option.

Using your air con for heat in a single room can reduce your heating bills, but remember you'll also need to factor in the cost to install air conditioning, in order to benefit from those savings.

How efficient are air conditioning units when it comes to heating?

'Using fitted air conditioning to heat a home can help to reduce a homeowner’s heating bills in winter because, compared to standard UK gas central heating systems, modern air conditioning units are typically more energy-efficient, as they can produce more heat than the energy they consume,' says Fernando de la Cruz Quintanilla.

Nicholas adds: 'In general air conditioning units in heating mode are very efficient because they work like heat pumps. They don't burn fuel like boilers, or convert electricity directly into heat like electric radiators, but instead they move heat from outside air into the home.'

FAQs

Do all air conditioners have heating capabilities?

Older air conditioning units may not offer heating capabilities, but most modern systems will (and it's something to check before you buy).

Beyond heating and cooling, many systems also have a dehumidifier mode as well as a fan mode, which can help ensure a comfortable living environment throughout every season.

It's important to note too that should you want to have and air con unit installed that's sole use is for cooling, then you will need to apply for planning permission. Units that offer both heating and cooling can usually be installed under permitted development.

Can you use a portable air conditioner for heating?

It's possible that a portable air con unit will have a heating mode, but it's unlikely to be as efficient as a fitted unit.

'If a portable AC unit has a heating mode, then that will likely work in the same way as an electric heater,' explains Nicholas. 'Plug in electric heaters only have a COP of 1, which means that you'll only ever get 1kWh of heat per 1kWh of electricity used. This means that it can be anywhere from 3 to 5 times more expensive to run than a fitted AC unit in heating mode, as they have a COP of 3-5.'

Can't decide between fitted and portable air con? I've tried both, and have a clear favourite.