AC / Heater Running Cost Calculator
Cooling and heating are the biggest lines on most power bills. Enter your unit's watts — or its BTU and EER — plus your usage pattern, and see the real air conditioner running cost per day, month, and season.
Window AC ~900–1,500 W · central AC ~3,000–4,000 W · space heater 750–1,500 W.
Watts = BTU ÷ EER.
AC compressors cycle: 60–80% typical. Heaters on full: 100%.
Cost per month
$0
0 kWh per day
Estimates only. Real duty cycles vary with weather, insulation, and thermostat settings.
How this AC running cost calculator works
It converts your unit's draw into daily kWh: kWh/day = watts × hours × duty cycle ÷ 1,000, then multiplies by your rate for the daily cost, by 30 for the month, and by your months of use for the season. If you only know the BTU rating, watts = BTU ÷ EER — a 12,000 BTU unit with EER 10 draws about 1,200 W.
The duty cycle is the key input most calculators skip: a compressor holding temperature runs 60–80% of the time, while a resistance heater on max runs 100%. That's why a "small" 1,500 W space heater often out-costs a bigger AC.
AC & heater cost FAQ
How much does an air conditioner cost to run per hour?
Divide the wattage by 1,000 and multiply by your rate and duty cycle. A 1,200 W window AC cycling at 70% costs about $0.13/hour at $0.15/kWh; central AC at 3,500 W runs $0.35–0.40/hour.
How do I convert BTU to watts for an AC?
Watts = BTU ÷ EER. A 12,000 BTU unit with an EER of 10 draws about 1,200 W. Higher EER or SEER means fewer watts for the same cooling.
What is a duty cycle and why does it matter?
The compressor cycles on and off to hold temperature, so it draws full power only part of the time. 60–80% is typical in hot weather; resistance heaters on full blast run at 100%.
Is electric heating more expensive than air conditioning?
Usually yes per hour: resistance heaters turn 1 kWh of electricity into 1 kWh of heat, while ACs and heat pumps move 2–4 kWh of heat per kWh of electricity. Heat pumps are the cheapest electric heat by far.