A fan costs much less to run than an air conditioner. If a breeze keeps you comfortable, start there. But a fan cannot lower the room temperature. If your home stays uncomfortably hot, especially overnight, air conditioning can do a job that a fan cannot.
Fan versus air conditioner: running-cost examples
The examples use 26p per kWh, close to Ofgem’s average Great Britain electricity rate of 26.32p/kWh for October to December 2026. The fan example uses 45 watts, matching the rated maximum of a Tristar pedestal fan. The air-conditioner figures are possible *average electricity use while cooling*, not their cooling capacity.
| Appliance and example electricity use | One hour | Eight hours | Eight hours daily for seven days |
|---|---|---|---|
| Pedestal fan: 45 W | 1.2p | 9p | 66p |
| Split air conditioner: average 0.7 kW | 18p | £1.46 | £10.19 |
| Portable air conditioner: average 1.2 kW | 31p | £2.50 | £17.47 |
Costs are rounded. Your fan’s power, air conditioner, weather and tariff will change the result. The figures show *extra electricity use*, so they exclude the standing charge you normally pay anyway. Northern Ireland has a separate electricity market; check your tariff through the Consumer Council.
As another reference, Energy Saving Trust’s 2026 comparison estimates 14p–30p for a fan running for 24 hours in Great Britain, compared with £4.62–£5 for a portable air conditioner. Its examples use different assumptions from our table, so the totals will not match exactly.
Why does a fan cost less?
A fan uses a small motor to move air. The breeze helps sweat evaporate and can make you feel cooler, but it does not remove heat from the room. Turn it off when nobody needs the airflow.
An air conditioner uses a compressor and fans to move heat outside. That takes more electricity, but it can lower the room temperature and usually remove some moisture. This difference matters more than the price per hour: a cheap fan cannot deliver the same cooling as AC.
When is a fan enough?
If you feel comfortable with a fan, there is no reason to pay for air conditioning just because the weather forecast says “heatwave”. A fan may work well in a shaded room that cools down after sunset, especially when only one person needs the breeze.
First, stop sunlight heating the room. Close blinds or curtains on sunny windows and keep windows shut while it is hotter outside than inside. When outdoor air becomes cooler, open windows if it is safe and let that air through. These steps can make your fan much more useful, and Energy Saving Trust recommends them.
When does a fan stop being enough?
Pay attention to the room and the people in it, not just the outdoor temperature. A fan may stop being enough if a bedroom stays hot through the night, shading and cooler-night air make little difference, or someone still feels unwell despite the breeze. A sunny top-floor flat may have a very different problem from a shaded ground-floor room.
Older people, young children and people with some health conditions face a greater risk during hot weather. If you cannot keep an occupied room comfortable, consider active cooling or spending time in a cooler place. If someone develops symptoms of heat exhaustion or heatstroke, follow NHS guidance promptly. Do not make that decision based on a few pounds of electricity.
If you are weighing up the purchase, our is air conditioning worth it? guide looks at the wider decision.
What does the 35°C fan warning mean?
The UK Health Security Agency’s home checklist recommends electric fans when the indoor air temperature is below 35°C. It also advises against aiming a fan directly at your body because that can contribute to dehydration.
This is not a target temperature for your home or a point at which you should finally consider cooling. You might need a cooler room long before it reaches 35°C. If the indoor air is that hot, do not rely on a fan alone; follow the current heat-health advice and find a cooler place. Check the temperature indoors rather than using the outdoor forecast as your guide.
Can you use a fan and air conditioning together?
Yes. A gentle fan can help air move through the room and make you comfortable at a higher thermostat setting. For example, you might prefer a fan with AC set to 25°C over AC alone at 23°C. Whether that saves electricity depends on how much less work the air conditioner does compared with the fan’s extra use, so avoid promises of a fixed saving.
If you use a portable air conditioner, seal the window opening around its exhaust hose. With either type of AC, keep outside windows and doors closed while cooling. You can switch to a fan and open the windows later when the air outside is cooler.
How can you spend less during a heatwave?
- Shade sunny windows before the room heats up.
- Use a fan if it keeps you comfortable; switch it off when you leave.
- Ventilate when it is cooler outside and safe to open windows.
- If you need AC, cool the occupied room rather than every room.
- Try a comfortable thermostat setting instead of automatically choosing the lowest one.
The best choice may change over the day. A fan could be enough in the morning, while a hot bedroom needs AC before sleep. For more on the actual electricity bill, see our guide to how much air conditioning costs to run; our UK temperature-setting guide covers choosing a comfortable thermostat setting.
For shading and ventilation throughout the day, use our home heatwave plan.
Estimate the cost for your room
You can calculate a fan’s approximate cost from its wattage: watts ÷ 1,000 × hours × your electricity price per kWh. At 26p/kWh, a 45 W fan running eight hours costs about 9p.
If you already have AC, CostToCool’s free Calculate my current setup route estimates its running cost using your room, system, schedule and tariff. If you are considering a system, free Plan cooling for my home estimates the capacity you may need and what a recommended setup could cost to run. Both are estimates; compare the result with what a fan achieves in your home.