Heat pumps can also cool your home – here’s what to know during the UK heatwave

When temperatures climb, most of us start thinking about fans, open windows, closed curtains and, if things get really sticky, whether it’s finally time to install air conditioning. Heat pumps don’t usually sit at the top of that list. In the UK, they’re still mostly discussed as a low-carbon alternative to a gas boiler: something that keeps your radiators warm and your hot water tank topped up throughout winter.

But that’s only part of the story. Some heat pumps can also work in reverse, moving heat out of your home rather than bringing it in. In other words, the same basic technology that can warm a house in January can, in the right setup, help cool it in July.

However, not every heat pump will cool your home, and not every heat pump installation will feel anything like air conditioning. An air-to-air heat pump is the clearest example of a system that can provide both heating and cooling. An air-to-water heat pump – the type more commonly installed in UK homes as a boiler replacement – is usually designed to heat radiators, underfloor heating and hot water. Some can provide cooling, but only if the system has been designed for it.

In theory, a heat pump can cool your home during a UK heatwave – but whether it can do so effectively depends on the type of heat pump and the way heat or cool air is distributed around your home.

Can a heat pump cool your home in summer?

Yes, some heat pumps can cool your home in summer. The best-known example is an air-to-air heat pump, which is essentially a reversible air conditioning system. In winter, it takes heat from outside air and brings it indoors. In summer, it can reverse that process, removing heat from inside the home and releasing it outside.

The Energy Saving Trust says air-to-air heat pumps can provide cooling during warm weather, although it advises households to consider other measures first, such as window shading and better ventilation, to minimise energy use.

The government has also recognised the cooling potential of these systems. In November 2025, it announced that the Boiler Upgrade Scheme would be expanded to include air-to-air heat pumps, describing them as technology that can keep homes warm in winter and cool in summer. The main caveat is that the term heat pump covers more than one type of system.

An air-to-air heat pump heats or cools the air directly, usually through one or more indoor units mounted on a wall, floor or ceiling. It’s well suited to cooling because it can blow cooler air into a room in much the same way as air conditioning.

An air-to-water heat pump works differently. This is the type many people have in mind when they think of replacing a gas boiler. It takes heat from the outside air and uses it to heat water for radiators, underfloor heating and a hot water cylinder. These systems are excellent for low-carbon heating, but they are not automatically designed to cool a home.

Ground source heat pumps can sometimes provide cooling too, including so-called passive cooling, where the relatively stable temperature underground is used to help take heat out of the home. But they’re less common in the UK and usually more expensive and disruptive to install.

So, if you’re wondering whether a heat pump can cool a home, the answer is: yes, but you need to ask what kind of heat pump, what indoor system it connects to and whether cooling has been factored into the installation.

How do heat pumps work in a heatwave?

A heat pump doesn’t create heat in the same way a gas boiler does. It moves heat from one place to another.

In heating mode, a heat pump extracts heat from outside air, the ground or water, then uses refrigerant, a compressor and heat exchangers to raise the temperature and move that heat indoors. The government’s heat pump explainer describes heat pumps as highly efficient electric appliances that transfer and intensify heat from outside air or the ground into a building.

In cooling mode, a reversible heat pump runs the process the other way. Instead of collecting heat outside and bringing it indoors, it collects heat from inside the home and releases it outside. The effect is similar to the way a fridge removes heat from its food compartment and releases it through the coils at the back.

The important point is that the heat still has to go somewhere. During a heatwave, the outdoor unit releases that unwanted indoor heat into the outside air. The harder the system has to work, and the hotter the air outside, the more electricity it may use to maintain a comfortable indoor temperature.

This is why shading, insulation and ventilation all play a role. A heat pump may be able to cool a room, but it will work more effectively if the home is not constantly gaining heat through sun-facing windows, poorly insulated loft spaces or appliances running during the hottest part of the day.

Cooling should also be designed properly. If a system is not set up for cooling, or if it sends chilled water through unsuitable radiators or pipework, it may perform poorly or create condensation. That’s why cooling should not be treated as a standard extra on a boiler-replacement heat pump. It’s something to raise with an installer at the design stage.

What the evidence says about heat pump cooling

There are four common claims around heat pumps and cooling. Some are true, while some need further context.

Claim one: Heat pumps can cool homes

This is true for some systems. Air-to-air heat pumps can provide both heating and cooling, and the government’s own air-to-air heat pump literature review describes them as systems that can provide cooling in summer while acting as both heating and air conditioning.

This is also why air-to-air heat pumps have been added to the Boiler Upgrade Scheme. The government said the expansion would give households access to technology that can provide warmth in winter and cooling in summer.

Claim two: A heat pump is basically air conditioning

This is partly true, but it depends on the system.

An air-to-air heat pump is closely related to air conditioning. In fact, many modern air conditioning units are heat pumps because they can both cool and heat.

But as explained above, an air-to-water heat pump is not the same as air conditioning because it heats water for your central heating and hot water system. Unless it has been specifically designed to provide cooling and is connected to suitable indoor equipment, it won’t cool your home like an air-con unit.

Claim three: Any heat pump can cool any home

This is false.

The cooling performance depends on the type of heat pump, the property, the indoor emitters, the controls, the insulation and the risk of condensation. A small flat with an air-to-air heat pump may be relatively easy to cool. A larger house with a standard air-to-water heat pump and radiators may not be.

That distinction is important because many UK heat pump installations are still designed primarily around replacing a boiler, not replacing air conditioning.

Claim four: Heat pump cooling will become more relevant in the UK

This looks increasingly likely.

The Climate Change Committee has warned that the UK needs to adapt to hotter conditions, including through better cooling in homes and public buildings. Its 2026 report says heat pumps that provide both low-carbon heating and cooling could help deliver cooling at lower cost and with less disruption, particularly in new-build homes.

That doesn’t mean every household should immediately install active cooling. But it does mean summer comfort is becoming part of the heat pump conversation, rather than just winter heating.

Are heat pumps more energy efficient?

Heat pumps are efficient because they move heat rather than generating it directly. A gas boiler burns fuel to create heat. An electric heater uses electricity to create heat. A heat pump uses electricity to move existing heat from one place to another.

That is why heat pumps can produce more heat energy than the electrical energy they use. The UK says heat pumps can produce around three units of heat for every unit of electricity they consume, although real-world performance depends on the system, property, and setup.

In cooling mode, an air-to-air heat pump operates in much the same way as an efficient air-conditioning unit. But that doesn’t mean cooling is free or that it will always be cheaper than other options. Running costs will depend on the heat pump’s efficiency, the outdoor temperature, your home’s insulation, how long the system runs for and the electricity tariff you’re on.

Using cooling sensibly also makes a difference. It will usually be more efficient to prevent a home from overheating in the first place than to let it become stiflingly hot and then try to cool it quickly. Shading, ventilation, curtains, blinds, insulation and avoiding heat-generating appliances during the hottest part of the day can all reduce the amount of active cooling needed.

For some households, pairing a heat pump with solar panels, a home battery or a smart electricity tariff could help reduce running costs. But this depends on when you use the system, how much electricity your solar panels generate, whether you can store it and what tariff you’re on.

Can a heat pump replace air conditioning?

An air-to-air heat pump can replace air conditioning in some homes because it is, in practical terms, a heating and cooling system. It may be particularly useful in flats, open-plan homes, small properties, home offices or individual rooms that regularly overheat.

It’s not always a whole-home solution, though. Larger homes may need multiple indoor units to cool different rooms. Air-to-air heat pumps also don’t usually provide hot water, so you may need a separate hot water system.

An air-to-water heat pump is a different proposition. It can replace a gas boiler for heating and hot water, and companies such as Octopus Energy install air source heat pumps as part of a wider low-carbon home heating system. But these installations are generally focused on heating and hot water, so you shouldn’t assume they will provide summer cooling unless that’s included in the design.

If cooling is a priority, ask the installer directly:

Does this heat pump have a cooling mode?
Is cooling enabled under the installation being proposed?
What indoor units or emitters are needed?
Will the system cool one room or the whole home?
How will condensation be managed?
Will cooling affect the warranty, controls or grant eligibility?

What are the downsides of using a heat pump for cooling?

The main downside is that cooling can be easy to misunderstand.

A homeowner may hear that heat pumps can cool and assume any heat pump will work like air conditioning. That’s not the case. Air-to-air systems are built for room cooling. Air-to-water systems may not be, especially if they’re connected to standard radiators.

Cooling can also add to electricity use during hot weather. That doesn’t mean it should never be used, particularly in homes that overheat or for people who are vulnerable to extreme heat. But it does mean passive cooling should come first where possible.

There are practical issues too. Indoor air-to-air units take up wall, floor or ceiling space. Outdoor units need a suitable location. Multiple rooms may require multiple units. Some systems recirculate indoor air rather than bringing fresh air into the home, so ventilation still matters.

For air-to-water systems, condensation is one of the biggest concerns. If surfaces get too cold in a humid home, moisture can form. That is why proper design, controls and compatible emitters are important.

When is the best time to install a heat pump?

The best time to install a heat pump is usually before your old boiler fails, rather than when you’re making a rushed decision in the middle of winter.

Summer can be a practical time to do the work because you’re less dependent on central heating. It also gives you time to think about the whole home, not just the outdoor unit. You may need radiator upgrades, pipework changes, a hot water cylinder, insulation improvements or a new electricity tariff.

If cooling is important to you, raise it at the first survey. Don’t wait until the system has been installed and then ask whether it can cool the house during the next heatwave.

In England and Wales, the Boiler Upgrade Scheme can help with the cost of replacing a fossil fuel heating system with a heat pump. The main scheme offers support for air source and ground source heat pumps, while the government has also announced support for air-to-air heat pumps as part of the scheme’s expansion. Octopus Energy says the Boiler Upgrade Scheme grant is applied to eligible heat pump quotes and that it handles the paperwork for customers through its heat pump installation service.

As ever, the details matter. Check eligibility, get more than one quote where possible, and make sure each installer explains exactly what their system will and won’t do.