Aircon vs Fan: What This Heatwave Is Really Costing You Per Hour
2026 has already delivered the hottest May on record, a ~40°C June heatwave, and now a third scorcher. The cooling maths at the current price cap (26.11p/kWh) is stark: a fan costs about 1p an hour, an air cooler 2–3p, and a portable aircon 21–37p. Here are the real numbers per hour, per night, and per month — and how to pick without regret. For your exact setup, our air conditioner cost calculator and fan vs AC comparison tool do the sums instantly.
Muhammad founded KilowattKit after spending hours trying to decode confusing electricity bills and realising there were no clear, jargon-free tools for ordinary homeowners. He researches energy rates, solar payback, EV charging, and heat pump economics across the US, UK, Canada, and Australia — sourcing every figure directly from official government and regulatory data.
🌡️ Key takeaways
- ✓A fan costs about 1p–1.6p per hour — a full night is ~10p, a whole month ~£3.
- ✓A portable aircon costs 21–37p per hour — £1.70–£2.90 a night, £50–£88 a month at 8 hours a day.
- ✓Evaporative air coolers sit in between (~2–3p/hr) but struggle in humid UK heat.
- ✓Fans cool you, not the room — only an air conditioner actually lowers the temperature.
- ✓All figures use the current Ofgem cap rate (Jul–Sep 2026): 26.11p/kWh.
The Cost Comparison at a Glance (July 2026 Rates)
| Device | Typical power | Per hour | Per night (8h) | Per month (8h/day) |
|---|---|---|---|---|
| Desk fan | 30–40W | ~1p | ~8p | ~£2.50 |
| Pedestal / tower fan | 40–60W | 1–1.6p | 8–13p | £2.50–£4 |
| Evaporative air cooler | 60–100W | ~2–3p | 13–21p | £4–£6 |
| Split / inverter aircon (bedroom) | 500–700W steady | 13–18p | £1.05–£1.45 | £31–£44 |
| Portable air conditioner | 800–1,400W | 21–37p | £1.70–£2.90 | £50–£88 |
Costs calculated at the Ofgem price cap electricity unit rate for July–September 2026 (26.11p/kWh, direct debit national average). Your regional rate and device wattage will vary — check the label on yours and run it through our appliance cost calculator.
How Much Does a Fan Cost to Run?
Almost nothing — and that surprises people every heatwave. Fans use tiny motors: 25–60 watts for nearly every household type. At 26.11p/kWh, a 40W fan costs 1.04p per hour. Run it all night, every night, for a month and you've spent about £2.50.
| Fan type | Watts | Cost per hour | All night (8h) |
|---|---|---|---|
| Small desk fan | 25–40W | 0.7–1p | 5–8p |
| Tower fan | 40–60W | 1–1.6p | 8–13p |
| Pedestal fan | 40–60W | 1–1.6p | 8–13p |
| Bladeless (Dyson-style) | 25–45W | 0.7–1.2p | 5–9p |
| Ceiling fan | 50–75W | 1.3–2p | 10–16p |
So no — fans do not use a lot of electricity. The catch is what they actually do: a fan doesn't lower the room temperature by a single degree. It cools you, by moving air across your skin and speeding up evaporation — worth a felt 3–4°C. Brilliant value while you're in the room; pointless when you're not.
How Much Does a Portable Air Conditioner Cost to Run?
This is where heatwave bills actually move. Portable air conditioners draw 800–1,400 watts — a small 8,000 BTU unit at the bottom of that range, a 12,000 BTU unit at the top. At the current cap rate:
Monthly figures assume 8 hours/day for 30 days at 26.11p/kWh. Poorly sealed exhaust hoses make real costs higher — the unit fights hot air leaking back in.
Two things make portable units worse than the label suggests: the exhaust hose must vent through a window (a bad seal lets hot air straight back in), and single-hose designs pull already-cooled air out of the room as they run. They're also the only realistic option that genuinely lowers the temperature in a UK home without installing a split system — which is exactly why they sell out every heatwave.
Model your unit, hours, and rate precisely with the air conditioner cost calculator.
Evaporative Cooler vs Air Conditioner: The In-Between Option
"Air coolers" (evaporative coolers) get marketed hard every heatwave as cheap aircon. They're neither a fan nor an air conditioner — and it pays to know the difference before spending £60–£150 on one.
Evaporative air cooler
- • Evaporates water to cool the airflow a few degrees
- • 60–100W → ~2–3p per hour
- • No exhaust hose, no installation
- • Works best in dry heat — weak in humid UK weather
- • Adds moisture to the room (can feel muggier)
Air conditioner
- • Refrigerant cycle genuinely lowers room temperature
- • 800–1,400W → 21–37p per hour (portable)
- • Needs window venting (portable) or installation (split)
- • Works in any humidity — and dehumidifies too
- • 10–15× the running cost of an air cooler
The honest verdict: in a humid UK heatwave — which is most of them — an evaporative cooler performs barely better than a fan costing a third as much to buy and run. In a dry spell it can take the edge off a small room for 2–3p an hour. If you need the room genuinely colder (say, for sleep or a home office under the roof), only an air conditioner does that.
Is It Cheaper to Run a Fan or an Air Conditioner?
The fan, always — by a factor of 20–30. The real question is whether a fan is enough:
- →Room below ~28°C, you just need comfort: fan wins. 1p/hour for a felt 3–4°C is unbeatable value.
- →Bedroom stuck at 30°C+ at midnight, can't sleep: this is aircon territory. The smart pattern: run it for 1–2 hours before bed (~50p), then switch to the fan overnight (~10p). Cool room, tiny bill.
- →Working from home in a loft office: a split/inverter system (13–18p/hour once at temperature) beats a portable unit on both cost and noise if you'll use it every summer.
Compare the two for your room size and hours with our fan vs AC calculator.
Cooling a Room Without Aircon: What Actually Works
Free and near-free tactics that beat buying hardware:
- 1Block heat before it enters: close blinds/curtains on sun-facing windows during the day — the single biggest free win (external shading is even better).
- 2Windows shut by day, open at night: once the outside air is cooler than inside (usually after ~9pm), cross-ventilate with windows on opposite sides.
- 3Point the fan at you, not the room — or out of a window at night to pump hot air out.
- 4Cut indoor heat sources: ovens, tumble dryers, and even TVs and gaming PCs add real heat — a heatwave is the week for cold dinners and the washing line.
- 5Cool yourself, not the house: cold water on wrists, damp sheet trick, cotton bedding — zero pence per hour.
Worked Example: One Heatwave Week
Bedroom cooling, 7 hot nights, at the July 2026 cap (26.11p/kWh):
The "smart combo" gets you a cooled room at bedtime for less than a quarter of the all-night aircon cost.
Enter your unit's wattage, your hours, and your rate — see the cost per hour, night, and month for any fan, cooler, or aircon. Free, no email, formula shown.