How much air con costs to run in the UK

How much does air con cost to run in the UK? Multiply the unit's electrical input in kilowatts by your unit rate. At the Ofgem price cap of 26.32p/kWh for 1 October to 31 December 2026, a 2.5 kW wall split works out at roughly 6–9p an hour on its seasonal rating. Compared like for like at full load, the split is about 19.5p an hour and a portable 25–31p.

Source: Ofgem, energy price cap unit rates and standing charges · checked 29 October 2026

How we read this GB averages for single-rate electricity paid by Direct Debit. The first two periods include 5% VAT and the third has none, so Ofgem says they are not directly comparable. Your own tariff may differ.

Show the numbers

Label	p/kWh	Note
Apr–Jun 2026	24.67	incl. 5% VAT
Jul–Sep 2026	26.11	incl. 5% VAT
Oct–Dec 2026	26.32	0% VAT

How much does air con cost to run per hour in the UK?

For a typical 2.5 kW wall-mounted split, the answer is single-digit pence per hour. We worked it from the makers' declared seasonal efficiency: 2.5 kW of cooling divided by SEER gives the electrical input, and that input times 26.32p gives the hourly cost.

Fujitsu's UK specification for the ASEH09KNCA declares SEER 7.40, which gives about 0.34 kW and 8.9p an hour. The Mitsubishi Electric MSZ-LN25 sheet declares SEER 10.5, giving about 0.24 kW and 6.3p.

Source: Ofgem price cap (26.32p/kWh) with declared figures from Fujitsu and Mitsubishi Electric spec sheets · checked 29 October 2026

How we read this Worked example, not a measurement. Inputs: 2.5 kW cooling output ÷ efficiency figure × 26.32p/kWh. Portable rows use the lowest EER for each label class, not a real product. SEER is a season average, so actual hours vary with weather and room.

Show the numbers

Label	p/hour	Note
Mitsubishi LN25, SEER 10.5	6.27	Most efficient sheet we read
Fujitsu ASEH09, SEER 7.40	8.89
Fujitsu ASEH09, EER 3.38	19.47	Full-load rating
Portable, single-duct class A (EER 2.60)	25.31
Portable, single-duct class C (EER 2.10)	31.33

Which electricity price should you plug in?

Use the unit rate printed on your own bill if you have one; otherwise use the cap. The Ofgem cap page gives 26.32p/kWh and a 54.83p daily standing charge from 1 October 2026. The standing charge is paid whether the unit runs or not, so leave it out of the cooling sum.

Summer prices were lower. Ofgem set 24.67p for April to June and 26.11p for July to September, both with 5% VAT included. Its July summary letter shows the typical dual-fuel bill climbing from £1,477 to £1,663 over that step. For this winter's VAT holiday on electricity, and the rate on installation, read how VAT applies to cooling kit.

How do you work out the cost from a spec sheet?

Find the cooling capacity in kW and an efficiency number, then divide. SEER is a seasonal figure that averages part-load and full-load running across a standard cooling season. EER is a single rating at full output, so it gives a higher, worst-hour cost.

For the same Fujitsu unit, SEER gives 8.9p an hour and EER gives 19.5p. The hour you actually pay for depends on how hard the unit is working, but SEER is the better guide to a season's average. Our SEER and SCOP page explains the label classes behind these numbers.

Why does a portable air conditioner cost more to run?

Portables are rated on EER, not SEER, and their label thresholds are lower. Under the GB energy label rules (Regulation 626/2011), a single-duct unit reaches class A at EER 2.60, while a split needs SEER 5.10 for the same letter.

There is a second cost the label does not show. The regulation defines a single-duct unit as one that takes its condenser air from the room and blows it outside. Warm outdoor air then leaks back in through gaps to replace it, so the room gets less cooling than the box says. The US Department of Energy's portable test procedure subtracts that infiltration and duct heat for this reason. A dual-hose or split unit avoids most of the loss.

What does a whole summer of air con cost to run?

It depends on hours more than on the unit. The chart below assumes six hours a day for 30 days, which is an illustration, not a typical-use figure.

Source: Ofgem price cap (26.32p/kWh) applied to the hourly costs in chart c2 · checked 29 October 2026

How we read this Worked example, not a measurement. Inputs: cost per hour from c2 × 180 hours. Your hours, room size and thermostat setting will change the total.

Show the numbers

Label	£	Note
Mitsubishi LN25	£11.28
Fujitsu ASEH09	£16.01
Portable class A	£45.55
Portable class C	£56.40

The Fujitsu sheet also states an annual cooling energy use of 118 kWh, based on the label's standard season. At 26.32p that comes to about £31 a year. Ofgem's October cap summary puts a typical home's whole dual-fuel bill at £1,723, so the cooling share is small.

Does using it for heating cost more than cooling?

Yes, because heating hours are far longer. The same Fujitsu sheet declares 763 kWh a year for average-climate heating, about £201 at 26.32p, against £31 for cooling.

Source: Fujitsu General UK, ASEH09KNCA specifications · checked 29 October 2026

How we read this Worked example, not a measurement. Inputs: declared annual kWh from the maker's sheet × 26.32p/kWh. Declared figures use a standard season, not your house or weather.

Show the numbers

Label	£ a year	Note
Cooling, 118 kWh	31.06
Heating, 763 kWh	200.82

Those heating pence replace whatever the room heater was burning before. If you are weighing a reverse-cycle split as main heating, see the Boiler Upgrade Scheme air-to-air grant.

Questions this data raises

Is it cheaper to leave air con on all day or switch it on when hot?

We have no measured UK data on this. The sums show cost follows hours of running, so a timer that keeps running to the hours the room is in use keeps the total down.

Does an Economy 7 or time-of-use tariff change the sums?

Yes, the method is the same but you swap in your own off-peak or peak pence per kWh. The cap figure of 26.32p is for single-rate electricity only.

How many watts does a small wall split draw?

On declared seasonal figures, a 2.5 kW unit averages roughly 240–340 W. At full output the Fujitsu EER of 3.38 implies about 740 W.

Does the standing charge go up if I add air conditioning?

No. The 54.83p daily charge is fixed by your tariff, so only the extra units used appear as added cost.

Sources for this page

1. Ofgem, energy price cap unit rates and standing charges ofgem.gov.uk
2. Mitsubishi Electric MSZ-LN25 sheet library.mitsubishielectric.co.uk
3. July summary letter ofgem.gov.uk
4. defines a single-duct unit legislation.gov.uk
5. October cap summary ofgem.gov.uk
6. Fujitsu General UK, ASEH09KNCA specifications generalww.com

All checked 29 October 2026. How we choose and read sources: Methods & sources.