A heat pump moves heat from one place to another, and that process can run in either direction. Pushed one way it warms your home in winter. Reversed, it pulls heat out of the rooms and dumps it outside, which is exactly what an air conditioner does. So the honest answer to whether a heat pump can cool your home is yes, but with a large caveat: only certain types are built to do it, and most of the air-to-water systems being fitted to British homes for heating are not set up for cooling at all. This guide explains which heat pumps cool, what cooling costs to run, and what to check before you assume your unit will keep you cool in a heatwave.
The short answer. Some heat pumps can cool, but most cannot. An air-to-air heat pump (effectively a fixed air conditioner) cools well and cheaply. An air-to-water system, the common UK heating type, only cools if it was specified with cooling and the right indoor units, and even then the effect is gentle. Running an air-to-air unit in cooling mode for the hottest months typically adds £40 to £120 to a summer's electricity bill at 26.11p per kWh.
How a heat pump cools (and why it is just air conditioning)
A heat pump and an air conditioner are the same machine. Both use a compressor and a refrigerant to move heat across a temperature difference. In heating mode the unit collects warmth from the outside air or ground and delivers it indoors. A reversing valve flips the refrigerant flow, so the unit collects heat from inside your rooms and rejects it outdoors instead. The room gets cooler, and the box outside blows out warm air.
Because cooling is the easier job (lifting heat from a warm room to slightly warmer outside air takes less effort than the reverse in deep winter), heat pumps tend to be efficient at it. The catch is mechanical: the unit needs the reversing valve fitted, the controls to allow a cooling setpoint, and indoor units that can handle the condensation that cold surfaces produce. Not every heat pump has all three. Our explainer on how heat pumps work covers the basics, and the difference between system types is set out in ground versus air source heat pumps.
Which type of heat pump can actually cool
This is where most of the confusion lives. The two common designs behave very differently in summer.
Air-to-air: cools well
An air-to-air heat pump blows conditioned air directly into the room through a wall-mounted indoor unit, the same hardware you see in offices and hotels abroad. These are reversible by design. Flip to cooling and they work exactly like a split air conditioner, because that is what they are. The indoor unit has a drain for the condensation it produces, so it takes real heat and humidity out of the air. If summer comfort matters to you, this is the type that delivers it.
Air-to-water: usually cannot, or only gently
An air-to-water heat pump is what most UK homes get when they replace a gas boiler. It heats water and sends it round radiators or underfloor pipes. Many of these units are heating only and will never cool. Some models are reversible and can send chilled water round the system, but there is a hard limit: if the water gets colder than the dew point of the room air, condensation forms on the radiators or the floor. Damp patches, puddles and mould follow. To stay safe the water has to be kept above roughly 16C, which gives only a mild take-the-edge-off effect rather than proper cooling.
To cool an air-to-water system properly you need fan coil units instead of plain radiators, each with its own condensate drain, plus controls that watch humidity. That is a specified-from-the-start design choice, not something you bolt on to an existing heating-only install. If you are deciding between system types, weigh this against the running-cost comparison in heat pump running cost versus a gas boiler.
What heat pump cooling costs to run
Cooling is cheap to run because heat pumps move several units of heat for every unit of electricity they draw. A reasonable air-to-air unit in cooling mode delivers roughly 3 to 4 kWh of cooling per kWh of electricity. The table below shows the electricity cost of running an air-to-air heat pump in cooling mode, alongside the alternatives, so you can see where it sits.
| Cooling method | Typical power draw | Cost per hour | 8 hours a day for 30 days |
|---|---|---|---|
| Air-to-air heat pump (one room, cooling mode) | ~0.5 kW | 13.1p | £31 |
| Air-to-air heat pump (whole open-plan area) | ~1.2 kW | 31.3p | £75 |
| Portable air conditioner | ~1.0 kW | 26.1p | £63 |
| Tower or pedestal fan | ~0.05 kW | 1.3p | £3 |
At 26.11p per kWh, Ofgem cap July to September 2026. Power draws are typical real-world averages once the compressor cycles, not nameplate maximums.
The headline is that an air-to-air heat pump cools a room for a similar or lower cost than a portable air conditioner, while doing the job better and more quietly, and it also heats in winter. A fan is far cheaper still but moves air rather than removing heat, so it only helps while you sit in the draught. For the full breakdown see air conditioning running cost and portable air conditioner versus a fan.
Grants, eligibility and the cooling question
The government's Boiler Upgrade Scheme gives a grant towards installing a heat pump in England and Wales, and from April 2026 the scheme was widened to include air-to-air heat pumps, which had previously been left out. That matters here because air-to-air is the type that actually cools well, so for the first time the grant can land on hardware that doubles as summer cooling.
The scheme is installer-led: an MCS-certified installer applies for the voucher on your behalf and takes it off your bill. Grant amounts and the rules on which technologies qualify have changed more than once, and the figure for air-to-water and air-to-air can differ, so check the current amounts and eligibility on the official Ofgem Boiler Upgrade Scheme page before you budget, since schemes change. Our evergreen write-ups, heat pump grants and cost and the Boiler Upgrade Scheme explained, walk through the process.
One thing the grant does not change: if you want cooling, you must tell the installer that up front so the system is specified for it. A standard heating-only quote will not give you a unit that cools, grant or no grant.
If you already have a heat pump, can you make it cool?
Maybe, and it costs nothing to find out. Work through these checks.
- Identify the type. Wall-mounted blowers in the rooms means air-to-air, which almost certainly cools. Radiators or underfloor heating fed from an outdoor box means air-to-water, which usually does not.
- Check the manual or controller. Look for a cooling or snowflake symbol, or a cooling setpoint in the menu. If it is there, the hardware supports it. If there is no cooling option anywhere, the reversing valve or the controls are not present and you cannot add cooling without major work.
- Ask the installer. Some air-to-water units are reversible but have cooling switched off in commissioning to avoid condensation risk. An installer can sometimes enable it, but only if your emitters and drains can cope, and expect only a gentle 2 to 3 degree drop rather than the sharp chill of a wall unit.
If your system cannot cool, you are not stuck. A single air-to-air unit in the room you use most, fans, blackout blinds and good night ventilation all help. Our guide to keeping cool without air conditioning sets out the cheap moves first, and fan running cost shows just how little a fan adds to the bill.
The bottom line
A heat pump can cool your home, but the type decides everything. An air-to-air heat pump is a reversible air conditioner that cools properly and cheaply, for roughly the cost of running a portable air conditioner, while also heating in winter. An air-to-water heat pump, the standard UK boiler replacement, mostly cannot cool, and where it can the effect is mild and limited by condensation risk.
So if summer comfort is part of why you are looking at a heat pump, ask specifically for an air-to-air system or an air-to-water system designed with fan coils for cooling, and confirm it in writing before the install. If you already have a heat pump, check the controller for a cooling mode before you assume it can or cannot do it. And if cooling is off the table, a fan, blinds and shade will always be the cheapest way to take the heat off a British summer.