How Much Does an Air Conditioner Cost to Run?

Running cost equals electrical input in kilowatts multiplied by time and your electricity unit rate. A portable air conditioner drawing 1,000W for five hours uses 5kWh. At an example rate of £0.25 per kWh, that is £1.25.

Replace the example rate with the price on your own bill.

Calculate my air conditioner running cost

Cooling output is not electrical input

A 9,000BTU/h label describes heat-removal capacity. It does not mean the appliance consumes 9,000BTU/h of electricity. Find rated input watts or kilowatts separately.

Efficiency, test conditions and operating mode determine the relationship between input and cooling output.

Worked examples

At £0.25 per kWh, an 800W unit at full input for four hours uses 3.2kWh and costs £0.80. A 1,100W unit for six hours uses 6.6kWh and costs £1.65. Seven identical six-hour sessions would cost £11.55 under that full-input assumption.

These are arithmetic examples, not price forecasts.

Ofgem explains that electricity is billed by kWh and that unit rates vary by tariff, region and payment method.

Use its current unit-rate information only as context; your bill is the right input.

The standing charge is paid regardless of this appliance and should not be assigned to one cooling session.

Thermostat cycling

Once the selected temperature is reached, the compressor may cycle while the fan continues or changes speed. Rated input multiplied by every clock hour can therefore overstate steady-state use.

On a very hot day, with an undersized machine or a leaking window seal, the compressor may run almost continuously. The manual describes model-specific behaviour.

Reduce load before adding capacity

Close suitable curtains or blinds before direct sun heats the room, limit unnecessary appliances and ventilate when outside air becomes cooler. Seal the exhaust opening as intended and close doors to unconditioned areas where safe.

Energy Saving Trust's cooling guidance puts heat prevention before appliance use.

For a measured answer, use a correctly rated plug-in energy monitor over representative hot days. Record kWh, temperature target and hours.

Use the SetupSelect calculator for scenarios and the air-conditioner finder to avoid costing an unsuitable capacity.

See what size air conditioner do I need? for the load factors.

Build a realistic usage range

One calculation is rarely enough. Work out a high-use case using rated input for every entered hour, then a lower case using fewer active hours.

The actual result may sit between them because a thermostat can cycle the compressor, but cycling depends on room load, set point and control design. Label both figures as scenarios rather than predictions.

For example, a 1.1kW input at £0.25/kWh costs £0.275 for each full-power hour. Four such hours would be £1.10 and eight would be £2.20.

If the fan continues after the compressor stops, consumption does not fall to zero; a plug-in energy monitor can show the combined real pattern for your unit.

Costs people often omit

• The purchase price of a compatible window seal or model-specific kit.
• Replacement filters or other maintenance required by the manual.
• The effect of an unsealed opening that lets warm air back into the room.
• Different electricity rates at different times of day.
• Extra hours caused by cooling a permanently connected space.

Do not compare an air conditioner's cost with a fan as if they deliver the same outcome. A fan mainly improves personal comfort through air movement and uses much less power; an air conditioner actively transfers heat outdoors.

First decide which outcome is required, then compare the cost of suitable options.

After purchase, record meter energy over a representative hot spell along with room conditions. That gives a more useful household figure than a retailer's fixed pence-per-hour claim based on an unknown tariff.