Appliance Energy Cost Calculator

Enter an appliance’s wattage, how many hours it runs each day, how many days you count in a month, and your electricity price.

How it works

Daily energy is (watts ÷ 1000) × hours per day. Monthly energy multiplies that by the days-per-month you enter (default 30). Monthly cost is monthly kWh × price. The annual figure uses 365 × daily kWh × price, so it does not assume twelve copies of the month length you typed. Nameplate watts are often higher than average draw — a fridge compressor does not run 24 hours at the rated wattage.

Formula

kWh/day = (watts ÷ 1000) × hours/day
kWh/month = kWh/day × days/month
Cost/month = kWh/month × price
Annual cost = kWh/day × 365 × price

Worked examples

100 W, 5 h/day, 30 days, 0.20 / kWh → 0.5 kWh/day, 15 kWh/month, 3.00 / month
100 W, 5 h/day, 0.20 / kWh → annual cost 36.50 (365 × 0.5 × 0.20)

Useful notes

Annual cost uses 365 days, not 12 × your monthly days setting.
Rated watts may not equal average watts. Use a measured figure if you have one.

FAQ

How do I estimate what an appliance costs per month?: kWh/day = (W ÷ 1000) × hours/day, then multiply by days in the month and by your kWh price.
Why doesn’t annual cost equal 12 × monthly cost?: Monthly cost uses the days/month you entered (often 30). Annual cost uses 365 days so a 30-day month is not silently treated as a 360-day year.
My fridge is 150 W. Do I enter 24 hours?: Only if the compressor truly runs all day. Duty cycle is often much lower. A measured kWh/day from a plug meter is better.

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