How to use the electricity cost calculator
The formula
kWh per day = watts × hours ÷ 1,000 and cost = kWh × rate. The monthly figure multiplies the daily cost by the days per month you enter; the yearly figure is twelve months of that.
How to use it
The wattage is printed on the appliance label or its manual (use the input watts, not a marketing figure). Hours per day is an honest average — a heater that cycles might only truly run 60% of the time it is switched on. Your rate is the per-kWh price on your electricity bill.
Good questions this answers
What does the old freezer in the garage cost a year? Is the space heater or the central heating cheaper for one room? What will a gaming PC add to the bill? Small daily numbers become surprisingly large annual ones.
Example
A 1,000 W heater used 5 hours a day at $0.20 per kWh: 1,000 × 5 ÷ 1,000 = 5 kWh per day, so $1.00 per day, about $30 per month at 30 days, and $360 per year. Enter those values above to see it.
Frequently asked questions
How is the cost worked out?
Energy per day is watts × hours ÷ 1,000, giving kilowatt-hours (kWh). Multiply by your rate: cost = kWh × price per kWh. Monthly uses the days-per-month you enter; yearly is monthly × 12.
Where do I find my electricity rate?
Your bill shows a price per kWh (sometimes called the unit rate). If there are several charges, divide the total variable part of the bill by the kWh used for a fair average.
My appliance cycles on and off. Is the estimate too high?
Possibly. A fridge or air conditioner rarely draws its full rated watts continuously. Use an average: if it runs at full power about half the time, enter half the hours.
Can I use a different currency?
Yes — the maths is identical. Enter your rate in pounds, euros, rupees, or any currency per kWh and read the results in that currency.
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