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Electricity Calculator
Estimate energy use, running cost and electric charge for an appliance from its power rating and how long it runs.
Electricity Calculator
Electrical energy, cost, charge, and capacitance calculations
E = P × t | Q = I × t | Cost = kWh × rate
W
hours
Result
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Step-by-Step
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Electricity is billed in kilowatt-hours: energy, not power. This calculator turns an appliance's wattage and daily hours into kWh used and the money it costs, so the bill can be predicted device by device instead of arriving as a surprise.
How to use this calculator
- Enter the appliance's power in watts.
- Enter the hours used per day and the number of days.
- Add your electricity price per kWh.
- Press calculate to see the energy used and its cost.
The vampire and the giant
Phantom loads (devices idling on standby) cost little each but run 8,760 hours a year. Heating, cooling and hot water are the giants: high watts for many hours. Ranking appliances with this calculator nearly always shows the same lesson: chase the giants first, the vampires second.
Frequently asked questions
What is a kilowatt-hour?
The energy used by a 1,000 W appliance running for one hour. A 100 W bulb takes 10 hours to use 1 kWh.
How do I calculate an appliance's running cost?
Watts ÷ 1,000 × hours used × price per kWh. That gives the cost for the period you entered.
Why is my bill high when my appliances seem small?
Usually one heating or cooling device with long hours, or many devices. The calculator's ranking approach, biggest first, finds the culprit faster than guessing.