Electricity Cost Calculator
What a device costs you per month and per year, based on its power draw and how long you run it.
Power
W
used
h/day
at
/kWh
How this is calculated
Power in watts is converted to kilowatt-hours (kWh) — the unit your electricity bill is priced in — then multiplied by your price per kWh.
kWh per day = watts / 1000 × hours per day
cost per day = kWh per day × price per kWh
cost per day = kWh per day × price per kWh
Example: a 100W device running 5 hours a day at $0.35/kWh → 0.5 kWh/day × $0.35 = $0.175/day, about $5.25/month.
Examples
- Laptop: 50W, 6 hours/day, $0.30/kWh → about $2.70/month.
- Old fridge: 150W running continuously (24h), $0.35/kWh → about $37.80/month.
- Space heater: 1500W, 3 hours/day, $0.35/kWh → about $47.25/month.
Frequently asked questions
Usually on a label on the device itself, in the manual, or on the manufacturer's spec sheet — look for a number in watts (W) or, for large appliances, kilowatts (kW).
On your electricity bill, usually listed as a rate per kWh. It can include or exclude taxes and fees depending on your provider.