Electricity Cost Calculator
Pick an appliance or type in the wattage, set how long it runs, and add your rate per kWh. You get the energy used and the cost per day, per month and per year.
Energy (kWh) = watts ÷ 1,000 × hours × days × number of devices. This ignores standby draw and assumes the appliance runs at its rated wattage whenever it is on — real heating and cooling devices cycle on and off, so treat the result as an upper bound for those. Your bill separates supply from delivery charges; use the all-in rate to match it.
Frequently asked questions
How do you calculate electricity cost?
Cost = power in kilowatts × hours used × your price per kWh. A 1,500 W space heater runs at 1.5 kW; four hours a day is 6 kWh; at $0.17 per kWh that is $1.02 a day, about $30.60 a month. Watts ÷ 1,000 gives kilowatts — the single step most people forget, which is why estimates come out a thousand times too big.
What is the average US electricity rate?
Residential rates in the US have recently averaged roughly 16–18 cents per kWh, but the spread is enormous: under 11 cents in states like Louisiana or Washington, well over 25 cents in California, Massachusetts and Hawaii. Your own bill is the only number that matters here — divide the total dollar amount by the kWh listed on the bill to get your all-in rate, which already includes supply, delivery and fixed fees.
Does a higher-wattage appliance always cost more to run?
No. What you pay for is energy, not power. A 1,500 W heater running two hours uses 3 kWh; a 150 W refrigerator cycling for 20 hours a day uses about 3 kWh as well, but spread across the whole day. Wattage tells you how fast it draws, hours tell you how long — only the product decides the bill. That is also why replacing an old fridge usually saves more than swapping light bulbs.
Why is my calculated cost lower than my actual bill?
Because a bill contains more than energy. Most utilities add a fixed monthly connection charge, taxes and sometimes demand or tiered-usage charges that rise in price per kWh as you use more. Devices on standby also draw power 24/7 — a house full of set-top boxes, chargers and game consoles can quietly add 50–100 kWh a month. Use this calculator per appliance, then compare the sum with your bill to find the gap.