UK split and multi-split calculator · tariff updated October 2026
Air conditioning running cost calculator.
Estimate fixed split or multi-split electricity use from the outdoor unit's rated input, an explicit inverter-load scenario and your tariff. No email required.
Starting tariff: 26.32p/kWh. GB average, Direct Debit, 1 October–31 December 2026. Use your billed rate, not this example; the cap does not cover Northern Ireland. Standing charge is excluded and no extra VAT is added. Ofgem source ↗ · tariff checked 7 October 2026.
2
Example result — replace the inputsElectricity use only. Installation, servicing and repairs are excluded.
Step 2 of 2Estimated monthly electricity cost
£22.0083.6 kWh across 20 use days0.52 kW average draw in this scenarioFull-load ceiling: £40.01 per month
The main estimate applies the 55% average-load assumption you entered. The ceiling keeps the same schedule but assumes every outdoor system draws its rated input continuously. A monitored or energy-label annual figure is stronger evidence than a guessed load percentage.
How the calculation works
Rated electrical input × load × schedule × unit rate.
The calculator multiplies the number of outdoor systems by rated electrical input, then applies the average-load percentage you choose. That estimated draw is multiplied by scheduled hours, use days, cooling months and your electricity unit rate.
The full-load figure deliberately ignores inverter modulation and thermostat cycling, so it acts as a visible ceiling for the same schedule. The starting rate is 26.32p/kWh; replace it with your bill's unit rate.
What changes the result
Factors worth checking before you decide.
Rated electrical input for the outdoor system—not advertised cooling output.
The system's real part-load modulation and thermostat cycling.
Room size, glazing, solar gain, insulation and air leakage.
Outdoor temperature and the indoor temperature you select.
How many outdoor systems operate at the same time.
Your electricity tariff, including any time-of-use period.
Worked examples
See how the assumptions move the answer.
The load setting makes the average draw explicit rather than pretending the compressor runs at one fixed level.
At 26.32p/kWh, that is about 25.00p for each continuous full-power hour.
Use the shared outdoor unit's electrical input; do not multiply it by the number of indoor heads.
Common questions
Questions homeowners ask before spending.
How much does fixed air conditioning cost to run in the UK?
Multiply the system's average electrical draw in kW by operating hours and your electricity unit rate. The result depends more on rated input, inverter load, room heat gain, thermostat setting and your tariff than on the number of indoor heads alone.
Is cooling capacity the same as electrical input power?
No. A system advertised as 3.5 kW cooling does not necessarily draw 3.5 kW of electricity. Use the rated electrical input from the outdoor-unit label, product fiche or installer data.
What load percentage should I enter for an inverter air conditioner?
There is no universal percentage. Use 100% to see a full-load ceiling, then compare lower scenarios only when you have metered data or a defensible expectation. Weather, room size, insulation, glazing and thermostat setting all change modulation.
How do I calculate a multi-split system?
Use the rated electrical input of the shared outdoor unit and enter one outdoor system. Do not multiply the outdoor-unit input by the number of indoor heads. If separate outdoor systems run together, add their input watts or enter the number of identical systems.
Does this include the electricity standing charge?
No. The standing charge is payable regardless of whether the air conditioner runs. This tool estimates the additional unit-rate cost attributable to cooling.
Sources and review trail
Transparent inputs, versioned model.
- Last reviewed
- 7 October 2026 (tariff); model reviewed 14 September 2026
- Model/version
- uk-fixed-ac-running-cost-2026.09.1