True cost of running a fan overnight in a heatwave | Personal Finance | Finance

With the UK heatwave in full scorching effect today – and even more hot weather coming on Tuesday – everyone’s sure to once again try to find ways to keep cool reliably and for as little as possible. The Met Office is predicting temperatures will continue to rise today, with sweltering 34C temperatures peaking today and on Tuesday.

Right now, the average Ofgem electricity unit costs 24.67p, but yours may be higher if you’re in a specific area, or have a tariff which changes price by day, or for example you use a credit meter, which usually charges more.

Next, you need to work out the kW output of your fan. You can do this by checking its wattage, which can be found on the fan or the instruction leaflet.

Currys explains: “Here’s the simple formula: Watts ÷ 1000 × kWh rate

“With the average UK tariff around 28p per kWh (2025), a 50 W fan costs about 1.4p per hour. Even a 100 W fan only costs 2.8p per hour. Compare that to an air conditioner, which can cost 30–40p per hour, and fans look like a bargain.”

At 2.8p per hour, left on for 10 hours a night, even the most energy consuming fan would cost you just 28p per night.

Across 90 days of summer, that would set you back £25.20.

Currys adds in its guidance: “Fans are one of the cheapest ways to stay cool in summer. Even running one all day costs less than your morning coffee.

“Fans are one of the most energy-efficient ways to stay cool. Most models use between 20 and 100 watts, depending on type and speed. That’s a fraction of what air conditioners or heaters consume, so you can enjoy a breeze without worrying about your energy bill.”