Most running cost figures you’ll see online are given without the sum behind them. That makes them hard to trust and impossible to apply to your own home. So this guide does it the other way round: it shows the method, states every assumption and uses the current Ofgem price cap rate, which you can check yourself.
The examples are illustrations, not promises. Your own cost depends on the unit, the room, the weather and how you use it.
The sum
Electricity is billed in kilowatt hours (kWh). One kWh is a load of one kilowatt running for one hour. So:
average power drawn (kW) × hours of use = kWh used
kWh used × unit rate (p/kWh) = cost
The only figures you need are how much power the unit draws on average while it runs, how long it runs and what you pay per kWh. The first is the hard one, because a modern inverter unit doesn’t draw a fixed amount. It ramps up to bring the room down to temperature, then slows to hold it there.
The unit rate to use
Ofgem’s price cap for 1 October to 31 December 2026 sets an average electricity unit rate of 26.32p per kWh for customers paying by Direct Debit, with a daily standing charge of 54.83p. Ofgem notes there is no VAT on electricity from 1 October 2026 to 31 March 2027. The cap changes every three months, and your own rate depends on your region and tariff, so check your bill and use your own figure if it’s different.
The standing charge is paid whether or not you run the air conditioning, so it isn’t part of the running cost.
Worked example: a bedroom on a warm night
Assumptions: a small wall-mounted unit averaging 0.6 kW over the night, running for 8 hours, at 26.32p per kWh.
- 0.6 kW × 8 hours = 4.8 kWh
- 4.8 kWh × 26.32p = 126p, or about £1.26 a night
- Over 40 warm nights in a summer: 40 × £1.26 = about £50
If your unit averages 0.4 kW instead, the night costs about 84p. If it averages 0.8 kW, about £1.68. That’s why the average draw matters more than anything else in the sum.
Want it done properly? AirCon Doctor installs, repairs and services air conditioning and heat pumps across London and the South East, from our base in East Grinstead. We’re an F-Gas certified company and NICEIC approved. Get a fixed-price quote.
Worked example: a living room in the afternoon
Assumptions: a larger unit averaging 1.0 kW, running 5 hours a day, at 26.32p per kWh.
- 1.0 kW × 5 hours = 5 kWh
- 5 kWh × 26.32p = about £1.32 a day
- Over 30 hot days: about £39
For a multi-split, add up the rooms that are running at the same time. Three rooms each averaging 0.6 kW for 4 hours use 7.2 kWh, which comes to about £1.90.
Finding your unit’s real figure
Every unit has a data sheet from its manufacturer. Look for the rated power input in cooling and in heating, given in kW. That’s what the unit draws at its rated output, under test conditions. In normal use an inverter unit spends much of its time below that, especially once the room is at temperature, so the rated input is a sensible upper figure to put into the sum.
Many modern units and apps also show energy use directly. If yours does, use the real reading: it beats any estimate. Our guide to SCOP, SEER and energy labels explains the other figures on the data sheet.
Heating mode
Most split systems also heat, working as an air-to-air heat pump. Their heating efficiency is shown as SCOP: the heat delivered for each unit of electricity over a season. A SCOP of 4 means about 4 kWh of heat for every 1 kWh of electricity.
Assumption: a SCOP of 4, at 26.32p per kWh. Each kWh of heat costs 26.32p ÷ 4 = about 6.6p. A plug-in or panel heater turns 1 kWh of electricity into 1 kWh of heat, so the same kWh of heat costs the full 26.32p. Check your own unit’s SCOP on its data sheet and divide your rate by it. To compare with gas, use your own gas rate divided by your boiler’s efficiency. Read more in using heat pump mode in winter.
How to keep the cost down
- Size it right. An undersized unit runs flat out for longer. Our sizing guide explains how we work it out.
- Pick a sensible set point. The bigger the gap between indoors and outdoors, the harder the unit works.
- Close curtains and blinds on sunny windows and keep doors shut to the rooms you’re cooling.
- Use timers to cool the room before bed rather than all afternoon.
- Keep filters clean and have the system serviced each year. A clogged filter makes the unit work harder.
- Look at your tariff. A time-of-use tariff can change the sum; see air conditioning and time-of-use tariffs.
Quick answers
How much does it cost to run air conditioning for an hour?
Multiply the average power drawn by your unit rate. A unit averaging 0.6 kW at the 26.32p Ofgem cap rate (October to December 2026) costs about 16p an hour.
Is air conditioning expensive to run in the UK?
For most homes the cost is modest because it runs on a limited number of hot days. Use the sum in this guide with your own unit’s figures to check.
Is it cheaper to heat with air conditioning than an electric heater?
Usually, yes. A unit with a SCOP of 4 delivers about four times as much heat per kWh of electricity as a panel heater.
Where do I find how much power my unit uses?
On the manufacturer’s data sheet under rated power input, or in the unit’s app if it reports energy use.
Related services
More advice
- How Much Does Air Conditioning Cost in the UK? 2026 Complete Guide
- Air Conditioning Energy Efficiency: SCOP, SEER and EPC Explained
- Running Air Conditioning and Heat Pumps on a Time-of-Use Tariff
- Air Conditioning in Winter: Using Heat Pump Mode Effectively
- Air Conditioning with Solar Panels: Can They Work Together?
- All advice
This guide is general information, checked against the sources linked on 30 October 2026. It isn’t legal, tax or financial advice. Rules, grants and product ranges change, so check the current position before you rely on it.