How the figure is calculated
Air conditioners are not priced from the nameplate here. The models in the list carry an energy figure measured under a standard test: in the US, ENERGY STAR lists annual kWh assuming 750 cooling hours a year (10 CFR 430, Appendix F); in Great Britain we use EU energy-label models, whose annual cooling figure assumes 350 hours and whose heating figure assumes 1,400 hours (Regulation 626/2011).
We divide that energy by those hours to get kWh per hour of real running, cycling included, then multiply by your price per kWh. The price is the Ofgem cap average or the EIA US average until you type your own.
What drives the cost
Capacity matters most: a 12,000 BTU/h window unit uses roughly half as much again as an 8,000 BTU/h one. Efficiency (CEER in the US, SEER and SCOP on the EU label) comes next, then the hours you run it and how hot it is outside. Heating with a split unit costs more per hour than cooling because it runs harder over a longer season.
Worked example
US: the LG LW8022IVSM (8,000 BTU/h, CEER 15.5) is listed at 387.1 kWh per 750-hour season. That is 0.516 kWh per hour, or 9.45¢ an hour at 18.31¢/kWh, and $70.88 for the season. A 12,000 BTU/h Frigidaire FHWW125WE1 at 600 kWh comes to $109.86, or $288.00 in Hawaii at 48.00¢/kWh.
GB: the Mitsubishi Electric MSZ-AP35VG (3.5 kW) uses 142 kWh for its 350-hour cooling season, 0.406 kWh an hour. At 26.32p/kWh that is about 10.68p an hour and £37.37 a season. Its heating season, 862 kWh over 1,400 hours, comes to £226.88.
Ways to pay less
Raise the set temperature a degree or two, shut doors to the rooms you are not cooling, and clean the filter. Use the hours box to see what one hour less a day saves over a season before you decide it is worth the sweat.
Questions
Why is the hourly cost lower than the wattage suggests?
The tested figure includes the compressor cycling down once the room is cool, so the average draw per hour is below the maximum.
Is the US price the price I pay?
It is the EIA average for July 2026 including taxes and fees. Pick your state or type the rate on your bill for a closer answer.
Does the result include the standing charge?
No. Daily standing charges are paid whether the unit is on or off, so they are never added.