How much does air conditioning cost to run?
Less than most people expect. At the Ofgem price cap for October to December 2026, a 2.5 kW bedroom unit costs about 7p to 17p an hour to cool, and well under £1 for a typical night. Below are the workings for 2.5, 3.5 and 5 kW units in cooling and heating, from real manufacturer data, plus how heating compares with gas.
- per kWh, Ofgem cap Oct to Dec 2026
- 26.32p
- an hour to cool with a 2.5 kW unit
- 7p–17p
- a night's cooling, 2.5 kW unit
- 55p–75p
- per kWh of heat, against 8.9p for gas
- 5.1p–5.7p
The formula
Cost per hour = electricity the unit draws (kW) × your price per kWh. The catch is that the size on the box isn't what it draws. A 3.5 kW unit delivers 3.5 kW of cooling but uses far less electricity to do it, because it moves heat rather than making it.
Electricity drawn = cooling or heating output ÷ efficiency. For example, Panasonic's spec sheet shows its value-range TZ35 drawing 0.98 kW while delivering 3.5 kW of cooling. At 26.32p per kWh that's 25.8p an hour, flat out. Most hours cost less, because inverter units slow down once the room reaches the set temperature.
Standing charges aren't part of the sum. You pay them whether the air conditioning runs or not.
Cooling cost per hour
Value range is the Panasonic TZ, premium is the Panasonic Etherea, using figures from Panasonic UK's spec sheets. Flat out uses the unit's power input at full nominal output. Seasonal uses full output at the seasonal efficiency (SEER), closer to a normal hour once the room has cooled.
| Unit size | Flat out, value | Flat out, premium | Seasonal, value | Seasonal, premium |
|---|---|---|---|---|
| 2.5 kW | 17.1p | 13.4p | 9.4p | 6.9p |
| 3.5 kW | 25.8p | 21.6p | 13.5p | 9.7p |
| 5 kW | 42.1p | 35.8p | 19.1p | 15.5p |
SEER used: TZ 7.0, 6.8 and 6.9; Etherea 9.5, 9.5 and 8.5. Electricity at 26.32p per kWh.
Heating cost per hour
The same units in heating mode, at their full nominal heat output. In heating, a 2.5 kW unit gives out about 3.3 to 3.4 kW of heat, a 3.5 kW unit about 4 kW and a 5 kW unit about 5.8 kW.
| Unit size | Flat out, value | Flat out, premium | Seasonal, value | Seasonal, premium |
|---|---|---|---|---|
| 2.5 kW | 20.8p | 18.4p | 18.9p | 17.2p |
| 3.5 kW | 26.1p | 23.2p | 22.9p | 20.2p |
| 5 kW | 44.7p | 36.8p | 33.9p | 31.8p |
SCOP used: TZ 4.6, 4.6 and 4.5; Etherea 5.2, 5.2 and 4.8. Once the room is warm, the unit usually runs well below full output.
Per night, per month and per year
Ranges run from the premium to the value model. A night is 8 hours of cooling at full output and seasonal efficiency. A month is 30 such nights. The yearly figures are each unit's energy label consumption, priced at the current cap.
| Unit size | 8-hour night, cooling | 30 nights, cooling | Year, cooling | Year, heating |
|---|---|---|---|---|
| 2.5 kW | 55p–75p | £17–£23 | £24–£33 | £184–£192 |
| 3.5 kW | 78p–£1.08 | £23–£33 | £34–£47 | £206–£224 |
| 5 kW | £1.24–£1.53 | £37–£46 | £54–£67 | £322–£327 |
Energy label figures use EU reference conditions: 350 hours a year at full cooling output, and a full heating season in an average European climate. Your use will differ.
SEER and SCOP explained
SEER (seasonal energy efficiency ratio) is the cooling delivered over a typical cooling season divided by the electricity used. SCOP (seasonal coefficient of performance) is the same idea for heating. A SCOP of 4.6 means 4.6 kWh of heat for every 1 kWh of electricity, averaged over a heating season. Both are printed on the product's energy label.
EER and COP are the same ratios measured at a single test point, usually at full output. Seasonal figures are more useful, because real use includes mild days and part-load running. Higher is better: the premium Etherea's SEER of 9.5 against the TZ's 7.0 is why it costs less per hour in the tables above.
Heating: air conditioning against gas
Cost per kWh of heat delivered into the room, at the Ofgem price cap unit rates for October to December 2026.
| Heat source | Efficiency assumed | Cost per kWh of heat |
|---|---|---|
| Air conditioning, premium range | SCOP 5.2 | 5.1p |
| Air conditioning, value range | SCOP 4.6 | 5.7p |
| Air conditioning, if efficiency falls to 3 | COP 3.0 | 8.8p |
| Gas boiler, well set up | 90% | 8.9p |
| Gas boiler, older or poorly set up | 85% | 9.4p |
| Plug-in or panel electric heater | 100% | 26.3p |
Workings: 26.32p ÷ SCOP for air conditioning, 7.97p ÷ boiler efficiency for gas.
Reading the gas comparison carefully
Per kWh of heat, air conditioning heating is cheaper than a typical gas boiler at today's cap, and about a fifth of the cost of plug-in electric heaters. But four things matter. First, seasonal figures are measured for an average European climate; efficiency drops on the coldest days. Second, boiler efficiency in real homes varies, which is why we show two figures.
Third, air conditioning heats air, not water. You still need your boiler or a cylinder for hot water, so you keep paying the gas standing charge of 29.68p a day unless you remove gas altogether. Fourth, these are unit prices only. If energy prices change, rerun the sums with the formula above.
Where it really pays is heating rooms that are otherwise warmed by plug-in heaters, or topping up rooms your boiler struggles with, like a loft or a cold extension.
How to keep running costs down
- Get the size right. An oversized unit cycles on and off and wastes energy; an undersized one runs flat out
- Clean the filters every few weeks in heavy use, and have the system serviced once a year
- Close windows and doors in the room you're cooling or heating
- Draw blinds or curtains on sunny windows during hot afternoons
- Use the timer or app to cool or warm the room before you need it, not all day
- Choose a moderate set temperature rather than the lowest the remote allows
- Keep leaves, bins and plants clear of the outdoor unit so air can flow
- Use the air conditioning for heating instead of plug-in electric heaters
- If you use it a lot, compare tariffs, including time-of-use ones
Running cost questions
Is air conditioning expensive to run in the UK?
Not usually. At the October to December 2026 price cap, a 2.5 kW bedroom unit costs about 55p to 75p for an 8-hour night of cooling at full output, and the energy label puts a year's cooling at about £24 to £33. Heating is a bigger cost because it runs for more hours.
Does a 3.5 kW air conditioner use 3.5 kW of electricity?
No. 3.5 kW is the cooling it delivers. Panasonic's value-range TZ35 draws 0.98 kW at full output, and less once the room is cool. That's about 26p an hour flat out at 26.32p per kWh.
How much does it cost to run air conditioning all night?
For a 2.5 kW unit, about 55p to 75p for 8 hours at full output and seasonal efficiency, depending on the model. If the room only needs a little cooling, it costs less. A 3.5 kW unit costs about 78p to £1.08.
Is it cheaper to leave air conditioning on all day?
Not all day in an empty room. Inverter units are most efficient when running steadily at low speed, so in a heatwave it often helps to keep a lived-in room at a steady temperature rather than repeatedly cooling it from hot. Use the timer to start cooling shortly before you need it.
Is heating with air conditioning cheaper than gas?
Per kWh of heat, yes at the current cap: about 5.1p to 5.7p with a modern split system, against about 8.9p for a gas boiler at 90% efficiency. It doesn't heat water, though, and the saving depends on your boiler and how cold the weather is.
Does air conditioning use gas?
No. It runs on electricity. The refrigerant inside is sealed in the pipes and isn't burned or used up.
What does SCOP mean on an air conditioner?
Seasonal coefficient of performance: the heat delivered over a heating season divided by the electricity used. A SCOP of 5.2 means 5.2 units of heat for every unit of electricity. SEER is the same measure for cooling.
Do premium units really save money?
They use less electricity for the same output. In our tables a premium 3.5 kW unit costs about 9.7p an hour to cool at seasonal efficiency, against 13.5p for a value unit. For occasional summer cooling the saving is small. For heating through the winter it adds up.