Keep your home cool in a heatwave by blocking out daytime heat and letting in cooler air at night. Our experts share their tips.
If your home feels too hot, these steps will help you cool down right now:
Fans are the cheapest appliance to help you stay cool at home. They don’t lower the room temperature, but they help keep your body cool.
Our energy experts have looked at the running costs of different cooling appliances:
| Cooling option | GB typical cost (24 hours use) | NI typical cost (24 hours use) | What it does | Best for |
|---|---|---|---|---|
| Fan (tower, desktop, pedestal) | £0.15 – £0.31 | £0.17 – £0.37 | Keeps your skin cool | Everyday cooling |
| Evaporative cooler | £0.28 – £0.40 | £0.17 – £0.37 | Adds moisture to cool nearby air | Small spaces |
| Portable air con | £4.84 – £6 | £6 – £7 | Actively cools the air | Very hot rooms |
If you need to cool your home quickly, these tips cost are easy to do and cost nothing.
When the air is cool outside and if it’s safe to do so, open windows all around your house to let cool air flow through. This is mostly likely to be at night.
If it’s a particularly warm day and the air is warmer outside than inside, close windows to keep the warmer air out.
It’s usually easier to stop heat coming into the home than it is to cool it down again. Close blinds and curtains when the sun is shining through a window.
Only open them when the sun has moved away as this will prevent heat coming through the glass.
No. Rather than cooling the air directly, fans create air movement that helps sweat to evaporate, keeping yourself cool. According to the NHS, electric fans are most effective when the temperature is below 35 °C.
More expensive tower, desktop and pedestal fans aren’t necessarily more efficient or cheaper to run than cheaper models either. Bladeless fans, which are often the most expensive to buy, have similar running costs to other models. So, the type of fan you choose largely depends on personal preference.
Due to their low energy use, fans have minimal CO2 emissions.
Top tip: using a small USB fan on your desk can be a cheap way to stay cool while working at your computer.
Although portable air conditioning units can cool rooms quickly, they’re significantly more expensive to buy than most fans and use much more energy.
Because air-con units use more energy than other cooling devices, running one also results in more CO2 emissions.
If you do need to use air conditioning, make sure you get the right size unit for the room you want to cool. Check that there are no gaps where the exhaust pipe goes out of the window, as this lets warm air back into the room.
Top tip: keep internal doors closed when an air-con unit is running to stop warm air entering from other parts of the house. When you turn the unit off, unplug it at the wall to stop it using energy while in standby mode.
Evaporative air coolers remove heat from the air to lower its temperature. Instead of using a refrigerant chemical like in an air conditioner, evaporative air coolers use a fan to move air over water. When water evaporates, it cools the air in the space near the unit.
A small, portable evaporative air cooler is likely to have a similar or slightly higher running cost compared to a typical fan. But they’re generally more expensive to buy.
Compared to portable air-con units, evaporative air coolers use less energy and have lower CO2 emissions.
Make sure you keep rooms well ventilated. Since these units evaporate water, they can increase the amount of moisture in the air in your home.
Top tip: keep internal doors closed while using an evaporative cooler. This will prevent warm air from entering the room and unplug when not in use.
Home insulation works in a similar way to a thermal mug or flask. Insulation slows the rate that heat escapes, keeping you warm in winter and cool in summer. Typical costs for wall, floor and loft or roof insulation depend on your home and the type of insulation you’re installing.
Adding solar film to your windows will help reduce the heating effect of sunlight shining through the glass. Costs vary depending on the film you choose as well as the size and number of windows you want to cover.
If you decide not to cover all of your windows, prioritise the ones that get the most sunlight. These include south facing windows, or those in rooms that get the warmest.
Air-to-air heat pumps are air conditioning units that can heat your home in winter and some models can also cool it during the summer.
They’re more common elsewhere in Europe than the UK. But as we see more frequent heatwaves and generally hotter summers, they may become a more common sight.
Check out our other summer energy saving tips.
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Last updated: 18 June 2026
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