How to use this calculator
- Enter or choose i know the.
- Enter or choose hours used per day.
- Enter or choose days used per year.
- Enter or choose average load.
- Enter or choose electricity price per kWh.
- The running cost per year updates as you type. Use Copy result or Share to keep it.
Method
Input kW = Cooling capacity (kW) ÷ EER (W/W); kWh per year = Input kW × Load% × Hours × Days; Cost = kWh × Price (1 kW = 3,412.142 BTU/h)
- EER
- cooling output divided by electrical input (W/W); a rating in BTU/h per W is divided by 3.412142
- Load%
- average share of full input power while switched on
Worked example
- Input power: 3.5 kW ÷ 3.5 = 1 kW.
- Energy: 1 kW × 70% × 8 h × 120 days = 672 kWh.
- Cost: 672 × 0.25 = 168 a year.
A 3.5 kW air conditioner with an EER of 3.5, used 8 hours a day for 120 days, costs about 168 a year at 0.25 per kWh.
What the result means
The load figure matters most: an inverter unit in a well-insulated room may average well under its rated input. For a better estimate, measure a typical day with a plug-in or smart meter and use that average with 100% load.
Assumptions and limits
- Efficiency and load are constant over the season.
- The tariff is a flat rate per kWh.
- Real consumption depends on outdoor temperature, insulation, thermostat setting and the unit’s part-load behaviour.
Questions
What is 1 ton of cooling in kW?
One refrigeration ton is 12,000 BTU/h, about 3.517 kW of cooling. Choose BTU/h and enter 12,000 per ton.
EER or SEER?
EER is measured at one test condition; seasonal ratios (SEER, ISEER) average over a typical season and usually give a more realistic yearly figure.