1,500 W for 4 hours a day
1.5 kW × 4 h = 6 kWh per day
Over 30 days, this uses 180 kWh. At an illustrative price of 0.20 per kWh, the energy cost is 36.00.
Home energy
Electricity Cost Calculator
Estimate the energy and cost of running an appliance or several identical devices.
Estimate electricity use and cost
Estimated electricity cost
Enter your power, daily usage, and price, then select Calculate.
All costs use the currency of your price per kWh.
- Combined power
- Energy per day
- Energy for your selected period
- Cost per day
- 30-day cost reference
- 365-day cost reference
The 30-day and 365-day references assume the same use every day, regardless of your selected period. They are not calendar-month bills.
Calculation steps
≈ marks display rounding. Calculations use the original values, not rounded steps. Fixed charges, taxes, tiered rates, and time-of-use pricing are not added.
Your inputs are processed in your browser and are not sent to a server. No electricity prices are fetched.
Energy and cost examples
Ten 10 W lights for 5 hours a day
0.01 × 10 × 5 = 0.5 kWh per day
At 0.20 per kWh, the daily cost is 0.10 and the 30-day cost is 3.00. Each light follows the same usage schedule.
100 W for half an hour
0.1 × 0.5 = 0.05 kWh
At 0.30 per kWh, the daily cost is 0.015, displayed as ≈ 0.02 at two decimal places. The unrounded cost over 30 days is 0.45.
Formula and assumptions
Daily energy in kWh = power in kW × hours per day × number of devices. Divide watts by 1,000 to get kilowatts. Multiply daily energy by the entered days, then by the price per kWh to get the estimated cost for that period.
A watt is a measure of power; a kilowatt-hour measures energy over time. A 1 kW appliance running for 2 hours uses 2 kWh. Entering a value already measured in kWh as watts would give the wrong result.
The calculation assumes a constant average power and one constant energy price. Devices with thermostats or changing loads can use much less than their maximum label power during some hours. Standby use outside the entered hours is excluded.
The 30-day and 365-day comparisons reuse the same daily schedule. The selected period can contain 1 to 366 days. These references do not model weekdays, holidays, seasonal use, calendar months, tiered pricing, fixed fees, or taxes.
Finite decimal inputs are multiplied with 100 significant digits, enough to preserve products within the stated limits. Only the displayed values are rounded, using 2, 4, 6, or 10 decimal places. Exact halfway values round away from zero; ≈ identifies display rounding. All costs remain estimates of usage under your assumptions.
References: U.S. Energy Information Administration: measuring electricity, U.S. Department of Energy: energy cost calculations, and measuring standby power.
Common questions
Where do I find the price per kWh?
Check the energy price on your bill or plan. Use the currency's main unit, such as 0.20 for 20 cents. If your tariff varies by time or usage band, calculate each portion separately or enter a suitable weighted average; this tool does not apply those rules automatically.
Does a 1,500 W appliance always draw that much power?
No. A label can describe rated or maximum power. Devices with changing loads or on/off cycles can draw a different average. Match the entered power to the stated hours, and use measured data when available.
How do I enter minutes?
Divide minutes by 60. For example, 15 minutes is 0.25 hours, 30 minutes is 0.5 hours, and 90 minutes is 1.5 hours. Daily usage cannot exceed 24 hours.
Why does the 365-day reference differ from my selected period?
The main result uses your selected number of days. The two references always use 30 and 365 days of the same daily usage. They do not infer your actual calendar or the number of working days.
Why might my actual bill be higher or lower?
This covers only the entered devices and usage. Other devices, standby consumption, tariff changes, taxes, fixed charges, and differences between rated and actual power can change your bill.