TL;DR
Fans cool people through air movement, not by reducing air temperature. Placing the fan to push hot air out of a window or pulling cooler night air in works better than running a fan in the centre of a closed room.
Fans cool people through air movement rather than by reducing room temperature, so placement during a heatwave significantly affects how well they work. Manufacturer guidance from established brands such as Dyson and the Energy Saving Trust both note that fans run in the wrong position can fail to deliver useful cooling.
How a fan actually cools you
Fans move air across the skin. The moving air helps sweat evaporate, which cools the body through the latent heat of evaporation. In an empty room a fan has minimal effect on air temperature; it only feels cooler when there is a person in the air stream.
Air conditioning, in contrast, removes heat from the room and dumps it outside through a refrigeration cycle. That is why a portable AC unit has a hose leading out of a window.
Two common placement mistakes
Running a fan in the centre of a closed room circulates the same warm air. The air feels cooler against the skin only because of evaporation, but the room itself does not get cooler.
Pointing a fan directly at a closed window during the day also fails. The window is the heat source, so the fan blows already-warmed air around the room.
Better placement strategies
At night, when outside air is cooler than inside, place a fan in or facing an open window pulling cooler air in. A second window open on the opposite side of the home creates a cross-draught that exchanges air with the outside.
During the day, with windows closed and curtains drawn, place a bowl of ice or a frozen water bottle in front of the fan. The air passing over the cold surface picks up some chill before reaching the room.
Tower fans, pedestal fans and ceiling fans
Tower fans take up less floor space and tend to be quieter than pedestal fans. Pedestal fans typically move more air but with more noise. Ceiling fans cover a wider area and pair well with air conditioning to spread cooled air.
Bladeless fans, including Dyson's Air Multiplier range, use the same air-movement principle as bladed fans. They are easier to clean and are often preferred for bedrooms and children's rooms, but cost more per unit.
Energy use and bills
Electric fans draw 40 to 90 watts depending on size and speed. Running a 60-watt fan continuously for 12 hours a day costs about 19p a day on the new Ofgem cap, or under £6 a month.
Comparison with portable air conditioning is stark. A typical 1,000-watt portable AC unit costs about £2.16 a day at the same level of use, or £65 a month. The right cooling choice depends on room size, occupancy and budget.
Key facts
- Fans cool through air movement, not temperature drop.
- 60-watt fan costs under £6 a month at heavy use.
- Night-time placement pulls cooler outside air in.
- Daytime use pairs well with frozen water bottles.
- Ceiling fans complement air conditioning.
FAQ
Does a fan actually cool the room?
No, fans move air rather than lowering temperature. The air feels cooler against the skin because moving air helps sweat evaporate, but the room itself does not cool unless air is exchanged with cooler outside air.
Where should I put a fan during a heatwave?
At night, in or facing an open window with another window open opposite to create a cross-draught. During the day, in a closed room with a bowl of ice or frozen water bottle in front of the fan.
Is a tower fan better than a pedestal fan?
Tower fans take less floor space and tend to be quieter; pedestal fans typically move more air but with more noise. The right choice depends on the room and noise tolerance.
How much does a fan cost to run?
About 19p a day for a 60-watt fan running continuously for 12 hours, or under £6 a month on the new Ofgem cap. Far cheaper than running a portable air conditioning unit.
