Running Cost Calculator

Your room

Enter the unit's input power in kW for the most accurate result (found on the spec sheet or energy label). Or enter the cooling capacity in BTU and the unit's EER rating instead.

Most accurate — use this if available from the spec sheet.

Used with EER when input power is not known.

Energy Efficiency Ratio — found on the unit's energy label or spec sheet.

Pre-filled with the current Ofgem price-cap rate. Adjust if you're on a different tariff.

Result

Enter the unit's power in kW, or its cooling capacity and EER, to see running costs.

How we calculated this

Formula: Input power (kW) × hours per day × days per year × rate (£/kWh)

When input power is not available, it is derived from cooling capacity and EER: Input power = Cooling capacity (W) ÷ EER, where cooling capacity in watts = BTU ÷ 3.412.

Based on the Ofgem cap for 2026-04-01–2026-06-30, last checked 2026-05-29. Source: https://www.ofgem.gov.uk/energy-price-cap

A typical 9,000 BTU portable air conditioner with an EER of 2.5 running 8 hours a day for 90 days costs roughly £30–£45 per year at current UK electricity rates — but figures vary widely depending on the unit's efficiency and your tariff.

Not sure what size unit you need? Use the BTU calculator first. Comparing two units on efficiency and purchase cost? Try the efficiency comparison calculator.