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Air conditioner running cost calculator

See what a portable air conditioner costs to run per hour, day and month. Pre-filled with the Ofgem price cap of 26.32p per kWh for 1 October to 31 December 2026.

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An electricity meter reading a few pounds, a plug and stacks of pound coins showing what an air conditioner costs to run

Your unit and usage

Printed on the box or rating plate

Most portable units are class A

Price cap: 26.32p

Running cost per day

£1.98

8 hours at about 942 W input power

Per hour
25p
Per month (20 days)
£39.67
Energy per day
7.5 kWh
A 40 W fan costs
1.1p/hr

Excludes your daily standing charge (54.83p), which you pay either way.

How to cut the bill

Running cost by unit size

Class A units (EER 2.8) with the compressor running continuously at 26.32p per kWh. Real cost is lower once the room is cool.

Estimated running cost of portable air conditioners by BTU rating at 26.32p per kWh
Unit sizePower drawnPer hour8 hours20 days of 8 hours
7,000 BTU0.73 kW19p£1.54£31
9,000 BTU0.94 kW25p£1.98£40
12,000 BTU1.26 kW33p£2.64£53
14,000 BTU1.47 kW39p£3.09£62

How the cost is worked out

Running cost is the electricity the unit draws, in kilowatts, multiplied by the hours it runs and your price per kilowatt hour (kWh):

cost = kW × hours × price per kWh

If you enter cooling capacity in BTU, the calculator divides by 3,412 to get kilowatts of cooling, then divides by the unit's energy efficiency ratio (EER) to get the electrical power. A class A portable unit has an EER between 2.6 and 3.1, so it uses about a third as much electricity as it delivers in cooling.

Want a cooler bill? Read running costs and energy efficiency for eight practical savings.

Frequently asked questions

How much does it cost to run an air conditioner per hour in the UK?

A typical 9,000 BTU portable air conditioner uses about 0.9 kW of electricity, which at 26.32p per kWh is about 25p an hour when the compressor runs continuously. Larger units cost more: about 33p an hour at 12,000 BTU.

What electricity price should I use?

Use the unit rate on your latest bill. If you are on a standard variable tariff, the Ofgem price cap for 1 October to 31 December 2026 averages 26.32p per kWh. Fixed and time-of-use tariffs can be higher or lower.

Why does the calculator ask for an energy class?

A portable unit’s BTU rating is its cooling output, not what it draws from the wall. The energy class gives the efficiency ratio (EER), which turns cooling into electrical power: a 9,000 BTU unit with an EER of 2.8 uses about 0.94 kW.

Is the real cost lower than the calculator shows?

Usually. Once the room reaches its target temperature the compressor switches off and only the fan runs. Choose “typical” or “hot day” in the last field to model that.

Does the calculator include the standing charge?

No. The daily standing charge (54.83p under the current price cap) is the same whether or not you run the air conditioner, so it is excluded.

How does the cost compare with a fan?

A 40 W fan costs about 1p an hour. It moves air but does not lower the temperature, so it suits mild days; an air conditioner is for when the room itself is too hot.

Cut the bill and choose well