Air Conditioning Running Costs UK
At the July 2026 price cap (~26p/kWh), a typical 2.5 kW bedroom unit costs about 18–23p an hour to run in cooling mode. Here are honest, worked numbers for every common unit size — cooling and heating — plus the settings that cut the bill.
What air conditioning actually costs to run
Air conditioners are rated by cooling output (2.5 kW, 3.5 kW, 5 kW), but they draw far less electricity than that, because heat pumps move heat rather than generate it. A 2.5 kW unit typically draws 0.7–0.9 kW from the mains — so at ~26p/kWh you pay roughly 18–23p per hour. Even heavy summer use rarely adds more than a modest amount to an annual bill; the table below shows realistic scenarios.
One thing to hold in mind: every figure on this page moves with your electricity unit rate. They are calculated at the July 2026 price cap of roughly 26p/kWh, but Ofgem resets the cap every quarter — the October to December 2026 level is announced in late August 2026 — and many households are on fixed or time-of-use tariffs that differ from the cap. If your rate is higher or lower, scale the costs up or down in proportion, and browse our wider air conditioning cost guides for the full picture.
Per hour and per summer, by unit size
Assumptions: electricity at ~26p/kWh (Ofgem cap, July 2026), typical power draw for a modern inverter unit at moderate load, and a "summer season" of around 300 hours' use (roughly 3–4 hours a day across the warm months).
| Unit size (cooling output) | Typical room | Power drawn | Cost per hour | Cost per summer (~300 hrs) |
|---|---|---|---|---|
| 2.5 kW | Bedroom, small office (up to ~15 m²) | 0.7–0.9 kW | 18–23p | ≈ £55–£70 |
| 3.5 kW | Living room, large bedroom (~15–25 m²) | 1.0–1.3 kW | 26–34p | ≈ £78–£100 |
| 5 kW | Open-plan space, conservatory (~25–35 m²) | 1.4–1.8 kW | 36–47p | ≈ £110–£140 |
Inverter units modulate: once the room reaches temperature the compressor slows right down, so real-world hourly averages often sit below these figures. Old fixed-speed units and cheap portable units cost noticeably more per hour of comfort.
Cooling vs heating: the honest comparison with gas
Modern splits are air-to-air heat pumps and heat with a seasonal efficiency (SCOP) of about 3.5–4: each kWh of electricity delivers 3.5–4 kWh of heat. At ~26p/kWh electricity, that works out at roughly 6.5–7.5p per kWh of delivered heat.
For comparison, mains gas costs about 7p/kWh, and a modern boiler at around 90% efficiency delivers heat at roughly 8–9p per kWh. So air-to-air heating is broadly similar to — often slightly cheaper than — gas central heating per unit of heat, and dramatically cheaper than plug-in electric heaters, which deliver heat at the full ~26p/kWh. Where air conditioning heating really wins is zoning: heating the one room you're using instead of the whole house. If you're weighing up whole-house options, see our air conditioning vs heat pump guide.
Efficiency tips that actually work
- Set 24–25°C in summer, not 18°C — every degree lower adds meaningfully to consumption. 24–25°C feels comfortable when it's 30°C outside.
- Clean the filters — clogged filters make the fan and compressor work harder. Rinse them monthly in heavy use; it takes five minutes.
- Shade the room — closing blinds or curtains against direct sun cuts the heat the unit has to remove before you've spent a penny.
- Keep doors and windows closed while cooling — you're paying to condition the air; don't swap it with the hallway.
- Use timers and presence sensors — most modern units schedule via app; cool the bedroom for bedtime, not all afternoon.
- Service annually — a serviced unit with correct refrigerant charge and clean coils runs at its rated efficiency; a neglected one quietly costs more every hour. See our servicing cost guide.
- Right-size at purchase — an undersized unit runs flat out all day; a correctly sized inverter unit cruises. Sizing is part of a proper survey.
- Match cooling to a cheaper tariff or your own solar — the hottest afternoons are also the sunniest, so a home with solar PV can run much of its cooling on self-generated electricity. On a time-of-use tariff, pre-cool the room during cheaper daytime or off-peak windows and let it coast through the pricey early-evening peak.
Realistic usage scenarios
| Scenario | Assumption | Approx. cost |
|---|---|---|
| Heatwave week, bedroom (2.5 kW) | 8 hrs/night × 7 nights ≈ 56 hrs | ≈ £10–£13 |
| Working from home, office (2.5 kW) | 6 hrs/day × 20 days ≈ 120 hrs | ≈ £22–£28 |
| Family living room, warm summer (3.5 kW) | 4 hrs/day × 90 days ≈ 360 hrs | ≈ £94–£122 |
| Winter heating, one room (3.5 kW output via heat pump) | 1,000 kWh of delivered heat | ≈ £65–£75 |
Same delivered heat via gas boiler: roughly £80–£90; via plug-in electric heater: roughly £260. Figures at July 2026 cap rates; your tariff may differ.
Frequently asked questions
Sources & methodology
- Electricity and gas unit rates based on the Ofgem price cap, July 2026 (typical dual-fuel bill £1,663/yr; electricity ~26p/kWh, gas ~7p/kWh).
- Power-draw and SCOP figures from manufacturer published specifications for current inverter split systems.
- Scenario costs are arithmetic from the stated assumptions, rounded; real consumption varies with weather, insulation and settings.
Get an efficient system sized for your room
The cheapest unit to run is the one sized and installed correctly. Air Con Surrey is a free matching service — we'll match you with vetted, F-Gas certified engineers who survey properly and quote competitively.