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Air Conditioner Running Cost Calculator

Enter your AC details to see the running cost.

How it is calculated

The tool first converts the nameplate rating into electrical power, then into money: power (kW) = (capacity in BTU/h ÷ EER) ÷ 1000, hourly cost = power × price per kWh, daily cost = hourly cost × hours per day, seasonal cost = daily cost × days per season. EER is BTU of cooling per hour for each watt drawn, so dividing by it gives watts. Hours per day must be between 0 and 24 and days per season between 0 and 366; capacity and EER must be above zero, otherwise no result is shown. Costs are shown in dollars, so enter your own electricity rate in the same currency unit. The tool assumes the compressor runs at full power the whole time; real units cycle on and off.

Worked example

A 12,000 BTU unit with EER 10, electricity at 0.15 per kWh, run 8 hours a day for 90 days. Power: 12,000 ÷ 10 = 1,200 W = 1.20 kW. Hourly cost: 1.20 × 0.15 = $0.18. Daily cost: 0.18 × 8 = $1.44. Seasonal cost: 1.44 × 90 = $129.60.

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Common mistakes

  • Entering the SEER rating where EER is requested; SEER is a seasonal average and is usually higher than EER, so the power draw comes out too low.
  • Typing capacity in tons or kW instead of BTU per hour (a 1-ton unit is about 12,000 BTU/h).
  • Entering the price in cents (15) instead of per kWh in currency units (0.15), which inflates every cost a hundredfold.
  • Using hours the room is occupied instead of hours the compressor actually runs; the tool assumes full power for every hour entered, so it overestimates for a thermostat-cycled unit.
  • Putting the number of months in the days field; it expects days, up to 366.

About this calculator

An air conditioner's efficiency is rated by its EER (Energy Efficiency Ratio) — BTU of cooling output divided by watts of electricity consumed. This calculator divides your AC's BTU capacity by its EER to get power draw in watts, converts that to kilowatt-hours over your chosen run time, and multiplies by your electricity price to estimate cost per hour, per day, and across a full cooling season.

A higher EER (or the related SEER rating for whole seasons) means the same cooling output for less electricity — a unit with EER 12 uses roughly 20% less power than one rated EER 10 for identical BTU output, which compounds into real savings over a summer of daily use. Homeowners comparing AC units before purchase, renters budgeting summer utility bills, and HVAC contractors use this calculator to translate a nameplate BTU/EER rating and local electricity rate into a concrete dollar figure.

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Comments (1)

  • Editorial team

    Look closely at the efficiency rating on the label. The EER field expects EER, and many units also list a higher seasonal rating called SEER; typing a SEER figure here would understate the power draw and the bill. Real units also cycle on and off, so the tool gives a ceiling for continuous running. How does the electricity price on your bill compare with the 0.17 shown as a default?

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