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

By AirconCalculator Team · Published 29 May 2026 · Last updated 29 May 2026

To estimate what an air conditioner costs to run, multiply its power draw in kilowatts by the hours you use it to get kilowatt-hours (kWh), then multiply by your electricity unit rate. As a working figure, the Ofgem price cap unit rate for April–June 2026 is around 24.67p per kWh for a typical direct-debit customer. So a 1 kW unit run for 5 hours costs roughly £1.23 in electricity.

Last updated: 29 May 2026. Unit rate based on the Ofgem energy price cap; your own tariff and region may differ.

What determines the running cost?

Three things drive the cost:

  1. Power draw (kW). Check the rated input power on the label or manual — usually in watts. Divide by 1,000 to get kilowatts. A typical mid-size portable might draw around 1 kW; larger units draw more.
  2. Hours of use. How long the unit actually runs. Many units cycle, so real-world use is often less than the time it is switched on.
  3. Unit rate (p/kWh). What you pay per kilowatt-hour of electricity, set by your tariff. The price-cap figure above is a reasonable default if you are unsure.

Worked example

Suppose you have a portable unit rated at 1,200 W (1.2 kW) and you run it for 6 hours on a hot evening:

  • Energy used: 1.2 kW × 6 hours = 7.2 kWh
  • Cost: 7.2 kWh × 24.67p = about £1.78 for the evening

Run that pattern across a 10-day heatwave and you are looking at roughly £18 for the spell. Over a cooler summer where you only use it occasionally, the total is far smaller — which is why estimating your real hours of use matters more than the headline wattage.

How can I keep running costs down?

  • Size the unit correctly. An undersized unit runs constantly; an oversized one short-cycles. Use our BTU calculator to match the unit to the room.
  • Cool the room you are in, not the whole house, and close internal doors.
  • Reduce heat gain by closing blinds on sunny windows during the day.
  • Use timers and eco modes so the unit is not running when you do not need it.
  • Choose an efficient model. A higher energy rating means more cooling per kWh, which adds up over a season.

Get a number for your unit

The figures above are illustrative. For a tailored estimate, enter your unit’s wattage, your typical hours and your own unit rate into the running cost calculator — it does the maths for you and lets you compare models side by side.

Frequently asked questions

How do I work out my air conditioner's running cost?
Take the unit's power draw in kilowatts (divide its watts by 1,000), multiply by the hours you run it, then multiply by your electricity unit rate in pence per kWh. For example, a 1 kW unit run for 5 hours uses 5 kWh; at around 24.67p/kWh that is roughly £1.23 for the session.
Is it cheaper to run a portable or a split air conditioner?
For the same cooling output, a fixed split system is usually cheaper to run because it tends to be more energy-efficient than a portable. However, portables avoid installation costs entirely, so the cheapest overall option depends on how often you actually use it.
Why is the unit rate I should use only a guide?
The electricity unit rate changes over time and varies by region, meter type and tariff. The figure here reflects the Ofgem price cap level for the stated period, but your own bill may differ. Always check your latest tariff for an accurate estimate.

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