THE UK heatwave has gone on for nearly a week leaving much of the country battling with near constant temperatures of over 30C.

The heatwave started with a bang on Friday with the country seeing its hottest day in August for 17 years, as temperatures reached more than 37C (96.8F) in south-east England.

Four days of sweltering temperatures have followed with Brits flocking to beaches, pools and parks to beat the heat.

Others have used fans to cool down – especially at night when sleeping conditions have been tough.

However, leaving fans on for a long time will increase your energy bills.

How much energy does a fan use up?

To work this out you need to find out how much electricity your fan uses.

Finding out the “wattage” of a fan will give you the answer and tell you the amount of power it’s using.

Then you need to find the total output you will have to turn that wattage into kilowatt hours.

To do this you need to use a bit of maths. First off divide the kilowatt hours by 1,000. This will give you how much output is used in one hour.

So if your fan is 70 watts output on its high setting and you always use this, divide 70 by 1000 = 0.07.

Then times this number by the number of hours you’ve used the fan.For example, if you’re using it for 12 hours per night – 0.07kW x 12 hours = 0.84kW output.

How much does it cost to leave a fan on overnight?

You’ve got your kilowatt output. Now you need to times it by the amount you pay for 1 kW of electricity.

Find this amount on your energy bill.

For example, if a kW costs 15p on your bill the sum will be: 0.84kW x 15  = 12.6p.The equation is: Cost = power (kilowatt) × time (hour) × cost of 1 kWh (pence).

According to Energy experts spoken to by HOAR the average cost of running a fan for 12 hours a night would come in at between 7.76p to 15.59p.

This means that by keeping your fan on for 12 hours every night during a month of 30.5 days, you’d see your energy bills rise by £3.55-£4.75.

Of course, costs will vary depending on the type of fan you have, how long you’re using it for and how much your energy costs. And the cost of your tariff.

Luckily, a fan is still far cheaper than air con. Just be aware that those with allergies and asthma have been warned that fans could be making their symptoms worse.

Do fans make a room cooler?

Although fans can’t make a room cooler they can make you feel cooler.

The air moving over your skin can lower your body temperature but won’t do much about the heat inside a room.

So if you don’t plan on being in the room there’s no point of leaving the fan on.