Cost to run a window fan
A window fan drawing 152.5 W costs 4.01p for each hour of running at 26.32p/kWh. Used 8 hours a day, 4 days a week, that comes to £5.58 a month.
An hour of running costs
4.01p an hour
That is 0.15 kWh. Used as set, it comes to £5.58 a month and £66.97 a year.
On the label or in the manual.
Standby, thermostats and off-peak use
A thermostat switches it on and off to hold a temperature. 100% if it runs flat out.
Drawn while plugged in and not running.
| Period | Cost | Energy | CO2e |
|---|---|---|---|
| An hour of running | 4.01p | 0.15 kWh | 33 g |
| A day, on average | 18.3p | 0.7 kWh | 152 g |
| A month | £5.58 | 21.2 kWh | 4.6 kg |
| A year | £66.97 | 254 kWh | 55.3 kg |
How we calculated this
Energy is power multiplied by time: 152.5 W running for an hour uses 0.15 kWh.
No source calls one figure typical, so the typical figure is the middle of Virginia Tech’s nameplate range for window fans, and the low and high figures are its ends.
The starting use for a window fan, 8 hours a day, 4 days a week, is where the calculator starts, not a measurement of your home: change it to how you use yours. A day is the average across the week, and a month is a twelfth of a 365-day year.
Electricity costs 26.32p/kWh. That is the published figure for the United Kingdom, 1 Oct – 31 Dec 2026, from Ofgem. Average for England, Scotland and Wales, paying by Direct Debit. No VAT on electricity from 1 October 2026 to 31 March 2027.
Standing charges are left out: you pay them whether or not the appliance runs.
Emissions use 0.217 kg CO2e per kWh, the lifecycle intensity of electricity generated in the United Kingdom in 2025, from Ember, via Our World in Data. Lifecycle means building the power stations and supplying their fuel are counted too. It is the grid’s average, not the particular power station an extra appliance brings on.
What drives the cost
A window fan pulls cooler outside air into a room, or pushes warm air out, so unlike a ceiling fan it can change the temperature of the room. At the middle of its range it draws 152.5 W and costs 4.01p an hour.
Also called: box fan, extractor window fan.
What it costs in the UK, Europe and the US
For a window fan used as typical (8 hours a day, 4 days a week), at each country’s published average electricity price.
| Country | Electricity price | An hour |
|---|---|---|
| United Kingdom | 26.32p/kWh | 4.01p |
| United States (average) | 18.19¢/kWh | 2.77¢ |
| Ireland | €0.4042/kWh | €0.062 |
| Germany | 0,3869 €/kWh | 0,059 € |
| France | 0,2561 €/kWh | 0,039 € |
| Spain | 0,2669 €/kWh | 0,041 € |
| Italy | 0,2966 €/kWh | 0,045 € |
| Netherlands | € 0,2558/kWh | € 0,039 |
Compared with similar appliances
| Appliance | Typical power | An hour | A year, typical use |
|---|---|---|---|
| Window fan | 152.5 W | 4.01p | £66.97 |
| Ceiling fan | 17.3 W | 0.46p | £7.09 |
| Window air conditioner | 666.7 W | 17.5p | £219.59 |
| Dehumidifier | 500 W | 13.2p | £288.20 |
How to spend less on it
- Run it in the evening and overnight, when the air outside is cooler than the air inside, and close the window during the hottest part of the day.
- Use a lower speed when the room is already cool: a slower fan draws less.
Questions
How much does a window fan cost to run per hour?
At 26.32p/kWh, a window fan drawing 152.5 W costs 4.01p for every hour of running at full power.
How much does a window fan cost to run a year?
Used 8 hours a day, 4 days a week, it costs about £66.97 a year at 26.32p/kWh, or £5.58 a month.
How many watts does a window fan use?
Most draw between 55 W and 250 W while running, and 152.5 W is typical. The rating is on the label or in the manual.
Is a window fan cheaper than air conditioning?
A window fan draws a fraction of what an air conditioner does, at 4.01p an hour here, but it can only bring in air that is as cool as the air outside. When it is hotter outside than in, it makes the room warmer.
Sources
- ENERGY SERIES: Estimating Appliance and Home Electronic Energy Use, Virginia Cooperative Extension, Virginia Tech, 26 February 2020. “Window = 55–250”
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