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How to use a fan in a heatwave UK

Updated: 21 October 2026

The fan is already plugged in and the room still feels hot. This is how to use a fan in a heatwave UK guidance actually describes: shade, windows, aim, and the point where you stop. Peter F. followed NHS, GOV.UK, Energy Saving Trust, CIBSE, the British Red Cross, and the Centre for Sustainable Energy, and checked them against the [room cooling comparison](/hub/cooling/room-cooling) on 20 October 2026. There was no lab test. A qualifying purchase can earn a commission at no extra cost to you. The method below assumes you already own something that only moves air.

The fan is already plugged in and the room still feels hot. This is how to use a fan in a heatwave UK guidance actually describes: shade, windows, aim, and the point where you stop. Peter F.

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On this page
  1. 1.A fan moves air; it does not cool the room
  2. 2.Shade first, then open windows only when outside is cooler
  3. 3.Aim the fan for the room, and stop at 35°C
  4. 4.When the fan should go off, and who should take over

A fan moves air; it does not cool the room

Energy Saving Trust says a fan moves air across your skin and does not lower the temperature of the room. CIBSE says the same: shade and ventilation come first. If you point a fan at trapped hot air, you mostly stir it. Sun-facing windows are how the heat got in. External shade is the stronger CIBSE step. Internal blinds still help, and you close them while the sun is on that glass. Turn the heating off, and switch off lights and kit you are not using. Energy Saving Trust puts a fan at about £0.14–£0.30 for 24 hours in Great Britain and about £0.17–£0.37 in Northern Ireland. An empty room does not become cooler because the fan is on. Model choice stays on the room cooling fan buying guide.

Shade first, then open windows only when outside is cooler

GOV.UK says open windows only when it is safe and the outside air is cooler. The British Red Cross describes the same daytime shut-up, with ventilation at night. Hotter outside air feeds the room. When outside is cooler, often at night, open more than one side if you can, and keep unsafe ground-floor windows shut. Place the fan to help that cross-flow. A pedestal or tower can do that. A tiny desk fan still hits one person. A bowl of water on the grille is not air conditioning. A tank cooler is the fan versus evaporative cooler page, and it is not a refrigerant unit.
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Aim the fan for the room, and stop at 35°C

GOV.UK says you may use a fan only when the air is below 35°C, and that you should not aim it directly at your body, because that can dehydrate you. NHS says electric fans can help below 35°C, alongside cold drinks and water on the skin. The British Red Cross uses the same threshold. Above it, stop using the fan as your cooling plan. Aim the stream into the room or along the cross-flow. Drink water. Move to a cooler room to sleep if you have one. Some local council pages warn against sleeping with a desk or pedestal fan left on. That is a local caution, not the NHS line. If someone is confused, very hot, or stops sweating, call 999. GOV.UK’s steps for heat exhaustion are a cooler place, fluids, and cool water on the skin, and they are not a substitute for emergency help.

When the fan should go off, and who should take over

Switch the fan off when the room is empty if you were only running it for a person. It will not pre-cool the air for the morning. Switch it off, and unplug it, if the plug, the lead, or the housing is hot, cracked, or sparking. Do not bypass a damaged plug with an adapter. A fixed install is an electrician’s job. A rented home that stays dangerously hot after you have shaded and ventilated, and the landlord will not act, is a matter for the council’s environmental health team, as GOV.UK describes.

Common questions

Does a fan lower the temperature of the room?
No. Energy Saving Trust and CIBSE both say a fan does not lower room temperature. It moves air so you feel cooler while the air is below 35°C. You will not find a degree drop for any fan on this shelf, and this page will not invent one. If the thermometer is the goal, you are looking at refrigerant cooling, which is a different comparison.
When should you open the windows if a fan is already running?
Open them only when the outside air is cooler than the room, and when it is safe to do so. GOV.UK and the British Red Cross describe daytime closing and night or early-morning opening. An open window onto hotter afternoon air works against you, however fast the fan spins. Try for air through the home, not a single pane beside the fan.
Where should you aim a fan in a UK heatwave?
Aim it to move air through the room, not directly at your body. GOV.UK warns that a direct aim can dehydrate you. Pair the fan with drinks and, if you need it, water on the skin, which is the NHS line. Do not follow advice that tells you to point the fan at yourself for hours. Shade and cooler outside air still come first.
At what temperature should you stop using the fan?
Stop using the fan as your cooling plan at 35°C. NHS, GOV.UK, and the British Red Cross use that threshold. Below it, a fan can help beside drinks and water on the skin. Above it, moving the air is not the plan. Call 999 if someone is confused, very hot, or stops sweating.
Should you leave a fan on in an empty room?
No, not if you hope it will cool the empty air. A fan cools people by moving air over skin. An empty room has no one to cool, and you still pay for the electricity. Energy Saving Trust’s 24-hour guide is about £0.14–£0.30 in Great Britain and about £0.17–£0.37 in Northern Ireland. Switch it off when you leave.

Related pages

Room cooling for the bedroom

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Best room cooling fan UK: top pick and who to skip

Room cooling fan buying guide: job, plug, then watts

Evaporative cooler vs fan UK: moisture and the tank

Sources

Public UK sources named below. amazon.co.uk prices, stars and review counts on these twelve listings are the figures stored for this comparison. Shelf date 20 October 2026. This is not a laboratory test.

  1. NHS heatwave advice (retrieved 20 October 2026)
  2. GOV.UK beat the heat checklist (retrieved 20 October 2026)
  3. Energy Saving Trust: keep your home cool (retrieved 20 October 2026)
  4. Ofgem price cap, 1 October to 31 December 2026 (retrieved 20 October 2026)
  5. CIBSE heatwave advice for residents (retrieved 20 October 2026)
  6. OPSS product safety report, T-SUN floor fan (retrieved 20 October 2026)
  7. British Red Cross: keep your home cool (retrieved 20 October 2026)
  8. Centre for Sustainable Energy: keep your home cool (retrieved 20 October 2026)