Research Desk · Original analysis · July 2026 energy prices
Every cooling product on sale this summer promises relief, and no listing tells you what that relief actually costs. We worked it out: purchase price plus a full summer of electricity, divided by the degrees of relief each product realistically delivers, giving one comparable number per product. The differences run to a factor of ten.
The one-line answer
A degree of relief from a £25 desk fan costs about £9 for the whole summer. The same degree from a mid-size portable air conditioner costs about £71, roughly eight times as much. Most of the products priced between the two work out as worse value than either.
The table
Assumptions: the July–September 2026 electricity price cap of 26.11p/kWh, and a “hot summer” of 300 running hours, which is roughly 7 hours a day across six weeks of hot spells. Relief is flagged as either measured, where the product genuinely lowers room temperature, or felt, where it lowers how hot you feel without changing the thermometer.
| Product | Typical price | Power | Cost/hour | Summer running cost | Relief | £ per °C, full summer |
|---|---|---|---|---|---|---|
| Desk fan | £25 | 35W | 0.9p | £2.74 | 3°C felt | £9.25 |
| Pedestal fan | £35 | 50W | 1.3p | £3.92 | 4°C felt | £9.73 |
| Tower fan | £60 | 60W | 1.6p | £4.70 | 3°C felt | £21.57 |
| Evaporative cooler | £70 | 80W | 2.1p | £6.27 | 1.5°C measured* | £50.85 |
| Portable AC, 9,000 BTU | £350 | 1,000W | 26.1p | £78.33 | 6°C measured | £71.39 |
| Portable AC, 7,000 BTU | £300 | 800W | 20.9p | £62.66 | 5°C measured | £72.53 |
| Portable AC, 12,000 BTU | £450 | 1,350W | 35.2p | £105.75 | 7°C measured | £79.39 |
| Dehumidifier (12L compressor) | £150 | 165W | 4.3p | £12.92 | 1.5°C felt† | £108.61 |
*Evaporative coolers can manage 2–5°C in dry air, but they need humidity below roughly 50% to work properly and UK summer humidity routinely sits at 60–70%, so our score reflects UK conditions. †A dehumidifier doesn’t cool the air (compressor units add slight warmth); it makes humid heat feel less oppressive. Portable AC running costs assume continuous running, and real bills are typically 20–40% lower because the compressor cycles off once the room reaches temperature.
What the number actually means
£-per-degree is the purchase price plus a summer’s electricity, divided by degrees of relief. The calculation deliberately loads the whole purchase price into one summer. That is harsh on expensive kit, but it matches the decision most people are actually making in a heatwave, which is what to buy today and what this summer will cost. Anyone who keeps a portable air conditioner for five summers will see its per-degree cost fall sharply, although the running cost returns every year.
Reading the table
The weakest value sits in the middle of the market. Premium tower fans, evaporative coolers and “air cooler” hybrids all deliver fan-level relief, or less, at two to five times a fan’s cost per degree. The evaporative cooler comes out worst for a typical UK summer at £51 per degree, because British humidity largely disables the mechanism it depends on.
There is also a clear split between felt and measured cooling. Moving air over skin costs about a penny an hour, while removing heat from a room costs twenty to thirty-five times that. Airflow solves daytime comfort for most people. The expensive option starts to justify itself in a bedroom that is still 28°C at midnight, where wind-chill helps less because the room itself needs to be cooler.
Among the air conditioners, the 9,000 BTU unit works out better per degree than the 7,000 BTU one, because an undersized unit runs flat out for a smaller result. The common mistake we see is buying too small and paying air-conditioning money for evaporative-cooler results. Our BTU sizing guide covers how to size correctly.
Methodology
Electricity at the Ofgem price cap for July–September 2026 (26.11p/kWh, direct debit average; regional rates vary slightly). Wattages are typical mid-market figures for each category. Relief figures come from the fan wind-chill effect of roughly 2–4°C, measured portable AC room drops of 5–8°C for a correctly sized unit, evaporative coolers scored at UK-realistic humidity, and dehumidifiers scored on comfort equivalence. Typical prices were checked in July 2026 and rounded; see individual product guides for current prices. We will re-run this table if the October price cap moves materially.
The combination we’d buy
For most households the best value is a combination: a £35 pedestal fan for the day and cooling bedding for the night. That comes to under £120 all-in, roughly £10 per degree of daytime relief, and costs nothing to run after dark. Air conditioning earns its place where the room itself has to be cooler, meaning bedrooms above 26°C at night, home offices in direct sun, and households where heat is a health hazard. Our too-hot-to-sleep guide covers the thresholds.
Sources
Ofgem energy price cap, July–September 2026; category wattage and running-cost figures cross-checked against published UK running-cost guides (Ideal Home, Uswitch and others, 2026); fan wind-chill and portable AC temperature-drop ranges from manufacturer specifications and independent testing coverage; our own running costs guide and portable air con analysis.