Energy-saving tips to keep your house cool during heatwaves

The UK now regularly experiences heatwaves, which many homes aren't built to withstand. While you might expect to use less energy and spend less money during the summer, many of us have invested (or are thinking of investing) in fans and air conditioning units. That means the cost of keeping cool can add up.

These energy-saving tips will help you keep your home cool in summer, no matter how warm the weather. The figures here use the average electricity unit price under the April 2026 price cap, which is 24.67p.

How much does it cost to run a fan?

On hot nights, many people will leave a fan running all night to cool the room down and make it easier to sleep. According to Uswitch research, a desktop electric fan costs approximately £5.67 per week to use if you have it on for nine hours every night.

If you want to make your fan more efficient, you could try placing a bowl of ice or a frozen water bottle in front of it to circulate the cooler air. To stop your room from warming up too much to start with, try keeping your curtains closed and windows open during the day where possible.

How much does it cost to run air conditioning?

While you might not think that home air conditioning is particularly common in the UK, spells of hot weather see significant increases in Google searches for portable air conditioning units.

According to Uswitch research, these units cost about £15.56 per week to run, assuming you're using them for nine hours every day.

How much does it cost to leave appliances on standby?

During the school half-term and summer holidays, it’s likely your kids will use more household energy while they keep themselves entertained watching TV and playing consoles.

However, the Energy Saving Trust estimates that the average household spends £45 per year leaving appliances on standby rather than turning them off.

If you want to reduce electricity usage, make sure appliances are turned off properly rather than being left on standby.

How much do showers cost?

It can be tempting to take more showers to cool off or freshen up during hot weather. But this uses more water and can also add to your energy bill.

A high-powered electric shower running for 10 minutes could add around 31p each time to your electricity bill, and the cost can quickly add up. If you could cut it to four minutes, it would cost 12p, saving you 19p.

How much does it cost to run outdoor patio heaters?

If you enjoy sitting out in your garden on a summer’s evening, you’ll know that the temperature can quickly drop, which is where patio heaters come in.

Prices will vary depending on the heater's power, but a 2.1kW electric patio heater used for five hours every day would cost £18.13 per week.

How to prepare for a heatwave

Heatwaves are usually announced in advance, so it's worth preparing if you know one will be starting in a few days.

• Whether you're using fans or air conditioning units, make sure they're working
• Install internal blinds or thick curtains if you don't already have them
• If you'd rather not go outside, make sure you're stocked with as much food as you'll need.

How to spend less while keeping cool during a heatwave

1. Create a cooling breeze. Place a bowl of ice cubes in front of an electric fan to create a refreshing breeze as it blows the ice-cooled air around the room.
2. Close the curtains. Keep your curtains shut during the day. It may be tempting to let the light in, but the sunshine will heat the room, turning your home into a greenhouse. 
3. Unplug the tech. The gadgets plugged in your home produce heat, including those that are on standby. Unplug them when you're not using them to keep the room cool. 
4. Take advantage of the daylight. Switch the lights off during the day. Lightbulbs release heat causing a room to get warmer, so turning them off can help reduce the overall temperature. With the sun setting late in the evening during summer you can keep the lights off for longer and the room cooler. 
5. Use a hot water bottle. You don’t have to use a hot water bottle just to keep warm. Instead, you can fill it with cold water to keep you cool during the night. 

Night-time cooling during a heatwave

The nights can be the most frustrating parts of a heatwave because of disrupted sleep. You can use a fan or air conditioning at night if the inside of your home is still overly warm, or try to find a cooler place to sleep. You can also open windows if the air feels cooler outside than in to try to get cooler air flowing through your home. Don't do this if the air is warmer than inside, because this will raise the temperature of your home.

Can you save by switching energy?

You may be able to switch to a cheaper deal, especially if you're on a standard variable tariff. This would mean that the cost of using all the appliances would be lower than the costs listed above. Compare energy deals to see what you might be able to switch to by clicking below.