Electrical Energy & Cost Calculator (E = Pt)
Electrical Energy & Cost Calculator (E = Pt)
Electrical energy usage is power multiplied by time, and electricity bills are based on kilowatt-hours (kWh) rather than joules. Enter the power rating of a device, how many hours it runs, and your electricity rate per kWh, and this calculator finds the total energy used and its cost.
A kilowatt-hour is a deliberately practical unit for household electricity, since the joule — the standard physics unit of energy — is inconveniently small for describing everyday appliance usage: a 1000 W appliance running for 5 hours uses exactly 5 kWh, a far more manageable number than the equivalent 18 million joules. This calculator is genuinely useful for a common real-world question — estimating what a specific appliance (a space heater, an AC unit, an EV charger) actually adds to a monthly electricity bill — by working directly from the device's power rating and your local electricity rate.
- Energy (kWh) = (Power in watts ÷ 1000) × time in hours, so a 1000 W appliance running for 5 hours uses (1000/1000) × 5 = 5 kWh.
- Cost = energy (kWh) × rate per kWh, so at 0.75.
- A kilowatt-hour is a much larger, more practical unit than a joule for household electricity - 1 kWh equals 3.6 million joules, which is why utility bills use kWh instead.
How do I calculate electricity cost?
Convert power to kW, multiply by the hours used to get kWh, then multiply by your electricity rate per kWh.
What does it cost to run a 1000 W appliance for 5 hours at $0.15/kWh?
(1000/1000) × 5 = 5 kWh, and 5 × 0.75.
Electrical Energy & Cost Calculator (E = Pt)
Electrical energy usage is power multiplied by time, and electricity bills are based on kilowatt-hours (kWh) rather than joules. Enter the power rating of a device, how many hours it runs, and your electricity rate per kWh, and this calculator finds the total energy used and its cost.
A kilowatt-hour is a deliberately practical unit for household electricity, since the joule — the standard physics unit of energy — is inconveniently small for describing everyday appliance usage: a 1000 W appliance running for 5 hours uses exactly 5 kWh, a far more manageable number than the equivalent 18 million joules. This calculator is genuinely useful for a common real-world question — estimating what a specific appliance (a space heater, an AC unit, an EV charger) actually adds to a monthly electricity bill — by working directly from the device's power rating and your local electricity rate.
- Energy (kWh) = (Power in watts ÷ 1000) × time in hours, so a 1000 W appliance running for 5 hours uses (1000/1000) × 5 = 5 kWh.
- Cost = energy (kWh) × rate per kWh, so at 0.75.
- A kilowatt-hour is a much larger, more practical unit than a joule for household electricity - 1 kWh equals 3.6 million joules, which is why utility bills use kWh instead.
How do I calculate electricity cost?
Convert power to kW, multiply by the hours used to get kWh, then multiply by your electricity rate per kWh.
What does it cost to run a 1000 W appliance for 5 hours at $0.15/kWh?
(1000/1000) × 5 = 5 kWh, and 5 × 0.75.