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Blog Post 29 June 2023 Updated 1 July 2024

Tips to keep your home cool this summer

Do you know how to keep your home cool in a heatwave without using too much extra electricity?

With more warm weather on the way, keep reading for tips from our energy experts on:

  1. How much it costs to use cooling appliances, including portable home air conditioning units.
  2. Home improvements you can make to lower indoor temperatures.
  3. No-cost changes to help you feel cooler at home without spending money.


Cooling appliances

Fans: tower, desktop, pedestal and bladeless


Typical cost for 24 hours of continuous use:  £0.20 – £0.40 


  • Using a fan can be an inexpensive way to keep cool in hot weather. Rather than cooling the air directly, fans create air movement which helps sweat to evaporate, meaning you stay cool. 
  • More expensive tower, desktop and pedestal fans aren’t necessarily more efficient or cheaper to run than cheaper models. Bladeless fans, which are often the most expensive to buy, have similar running costs to other models. The type of fan you choose therefore largely depends on personal preference. 
  • Due to their low energy use, fan have minimal carbon emissions. For example, using one fan for an average of eight hours a day throughout the summer would generate around 10kg of carbon dioxide emissions (roughly equivalent to driving from York to Leeds), or less depending on the model.


Top tip: using a small USB fan on your desk can be a cheap way to stay cool while working at a computer, with running costs as low as £0.01 per day. 


Portable air conditioning units 


Typical cost for 24 hours of continuous use: £6.00 


  • Like fans, air-con units create air flow, but they also remove heat from the air to lower the temperature of a room. 
  • Portable air conditioning units are significantly more expensive to buy than most fans and use much more energy. Running a portable air conditioning unit continuously for 24 hours would cost more than 20 times as much as running a typical freestanding fan for the same amount of time. 
  • Fitted air conditioning units aren’t commonly found in UK homes.


  • Because air-con units use more energy than other cooling devices, running one also results in more carbon emissions. Using a portable air-con unit for an average of eight hours a day during the summer would result in a total of around 140kg of carbon dioxide emissions, the same as a seat on a flight from Belfast to Paris. 
  • If you do need to use air conditioning, make sure you get the right size unit for the room you’ll be cooling and check that there are no gaps where the exhaust pipe goes out of the window, as this would let 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 prevent any energy potentially being used in standby mode. 



Evaporative air coolers 


Typical cost for 24 hours of continuous use: £0.40 


  • Like air conditioning units, 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 draw 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 are generally more expensive to buy. 
  • Compared to portable air-con units, evaporative air coolers use less energy. Using one for an average of eight hours a day during the summer would result in similar carbon emissions to using a fan – around 10kg of carbon dioxide, roughly the same as driving from York to Leeds.  
  • As they are evaporating water, these units can increase the amount of moisture in the air in your home so make sure to keep rooms well ventilated. 


Top tip: keep internal doors closed while using an evaporative cooler to prevent warm air from entering the room and unplug when not in use.  



Investments you can make to keep your home cool

  • Topping up your insulation
    Insulation in a home works in a similar way to a thermal mug or flask: a flask slows the rate that heat escapes or gets into the liquid, keeping hot drinks hot and cold drinks cold. Insulation in a house works in the same way and will help to keep a home cool in summer and warm in winter. 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 windows
    Adding solar control film to your windows, either yourself or by a professional, will help reduce the heating effect of sunlight shining through the glass. Costs will vary depending on the film you choose as well as the size and number of windows you choose to cover. If you decide not to cover all of your windows, prioritise the ones that receive the most sunlight, such as south facing windows, or those in rooms that get the warmest. 

Zero-cost ways to cool your home

  • Open your windows: this sounds obvious, but you have to open the right windows at the right time. When the air is cool outside, opening windows at all sides of your house will let cool air flow through.  If it’s a particularly warm day and the air is warmer outside than inside, close windows to keep the warmer air out.


  • Closing blinds and curtains: this is also a matter of timing. It’s usually easier to stop heat entering a 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 from the sunlight coming through the glass. 

Last updated: 1 July 2024