If you're weighing up whether to add cooling to your heat pump, cost usually comes up twice once for the installation, and once as a quiet worry that never gets answered: what will it actually cost to run every summer? We've already covered the installation side in Can I Add Cooling to My Existing Heat Pump?, so this guide focuses purely on running costs the number that actually shows up on your electricity bill once cooling is live.

The short answer

Running a heat pump in cooling mode typically costs somewhere between 75p and £1.50 per day during genuinely hot weather, based on 4-6 hours of active cooling. Across a typical UK summer which usually means somewhere between 30 and 50 days where you'd actually want cooling on that works out to roughly £25 to £90 for the whole season. Compare that to a portable air conditioning unit running the same hours, which is often two to three times less efficient and considerably noisier, and heat pump cooling starts to look like one of the cheapest ways to stay comfortable in a UK summer.

Why it's so much cheaper than most people expect

The reason cooling costs so little compared to heating is simple: in the UK, you're rarely cooling against a large temperature difference. Heating your home in January might mean fighting a 20°C gap between outside and your target indoor temperature. Cooling in July is usually closing a gap of 5-8°C at most, even during a proper heatwave. Less work for the compressor means less electricity drawn, which is why most homeowners are pleasantly surprised the first summer their system runs in cooling mode. We touched on this exact seasonal swing in Do Heat Pumps Cost More to Run in Winter Than Summer? summer is already your heat pump's cheapest season even before cooling enters the picture, since space heating drops away almost entirely and the system is mostly just cycling the hot water cylinder.

What actually changes your number

The £25-£90 range is wide because a handful of things genuinely move it:

System type. Air-to-air systems cool more directly and efficiently closer to how a conventional air conditioner performs. Air-to-water systems cooling through underfloor pipework are gentler (typically only 2-4°C of cooling) and use less electricity, while those cooling through fan coil units sit somewhere in between, using more electricity than underfloor cooling but delivering noticeably faster, more noticeable relief in the room.

How many rooms you're cooling. Cooling one bedroom overnight is a very different electricity draw to running cooling across an entire ground floor all afternoon. If you're deciding between a single-room retrofit or a whole-house setup, our guide on Can a Heat Pump Cool Every Room in the House? walks through what that decision actually involves.

Your electricity tariff. If you're on a time-of-use or overnight tariff, running cooling in the evening rather than through peak afternoon hours can meaningfully change the cost, in the same way it does for heating.

How well the system was designed. This is the one homeowners underestimate most. A cooling setup with the wrong dew point sensor configuration, an undersized fan coil unit, or pipework that wasn't properly assessed for cooling duty doesn't just risk condensation problems it also runs less efficiently, which shows up directly as a higher bill. If you're not sure whether your setup accounts for this properly, our article Do I Need a Dew Point Sensor for Heat Pump Cooling? explains why this one component affects both safety and running cost.

Why this is genuinely one of the cheapest cooling options available

Portable air conditioning units are notoriously inefficient most single-hose portable units lose a significant amount of their cooling effect pulling in warm air to replace what they exhaust, meaning they run longer and harder to achieve the same result. A heat pump already installed for heating that's properly set up for cooling avoids that problem entirely, since it's a purpose-built, correctly sized system rather than a temporary bolt-on. If you're weighing up a heat pump's cooling mode against buying a portable air conditioner instead, our comparison in Is Heat Pump Cooling Better Than Air Conditioning? covers the efficiency gap in more detail.

Getting an accurate figure for your own home

Every number in this guide is a genuine UK range, not a figure specific to your property. The real cost depends on your system, your emitters, how many rooms you want cooled, and how the setup was commissioned which is exactly what we assess in our Heat Pump Cooling Assessment. As part of that £295 review, we confirm whether your system is genuinely suitable for cooling, provide the wiring diagrams and controller settings your installer needs, and support the commissioning process so the system runs efficiently from day one rather than finding out after a summer of higher-than-expected bills that something in the design wasn't quite right.

FAQ

Does cooling mode use a lot more electricity than heating?
No for most UK homes, cooling uses considerably less electricity than heating, simply because the temperature gap the system has to work against is much smaller in summer than in winter.

Will adding cooling make my winter heating bills worse?
No. Cooling and heating are separate operating modes; running cooling in summer has no effect on your heating performance or costs the following winter.

Is a whole-house cooling setup much more expensive to run than cooling one room?
Yes, proportionally more rooms means more electricity draw. Most homeowners start with the rooms they actually need cooled (usually bedrooms and the main living space) rather than cooling the whole house by default.