Estimate the electricity an appliance uses and its variable running cost. Enter power in watts or kilowatts, your active hours per day, the number of days, and your own electricity usage rate.
Plan your energy use
What will it cost to run?
Enter an appliance’s power, active hours, and your electricity rate. Start with the example below, then adjust it to your home.
How to use your estimate
The result is a scenario based on your inputs, rather than a measurement or a complete utility bill. Change one input at a time to see how power, active hours, days, and price affect the result. Switching W/kW or currency/cents converts the entered number to preserve the same scenario.
For a cycling appliance such as a refrigerator or thermostat-controlled heater, use measured average power or the time it actively draws the stated power. Do not assume it runs continuously at its maximum rating. If your bill has different prices by time or usage tier, this flat-rate estimate cannot reproduce those charges.
Purpose
Estimate one appliance’s energy use and variable electricity cost over a chosen number of days. General principles; no regional tariff database is used.
Inputs
Power: zero or a positive number, in W or kW.
Active hours per day: 0–24; fractions are accepted.
Days: a whole number, zero or greater.
Rate: zero or a positive number, in the selected currency/kWh or cents (one hundredth of that currency)/kWh.
Currency labels: USD, CAD, AUD, EUR, or GBP. Changing the currency label does not convert prices. Extremely large combinations are rejected.
Units
W, kW, hours/day, days, kWh, currency/kWh or cents/kWh. 1 kW = 1,000 W; 100 cents = 1 currency unit (GBP uses pence). USD is the illustrative default; use a matching tariff for the chosen currency.
Currency
USD
Formula / model
Daily energy (kWh) = power (W) / 1,000 × active hours per day
Period energy (kWh) = daily energy × number of days
Usage cost = period energy × rate per kWh
If power is entered in kW, no division by 1,000 is needed. If the rate is entered in cents/pence, divide it by 100 before multiplying. Results are calculated before display rounding.Model version
electricity-cost-v1.0.0
Assumptions & limitations
Power is constant during the entered active hours, and the same schedule applies on each entered day. The entered flat variable rate applies to all calculated energy.
Fixed charges, taxes, demand charges, tiered pricing, time-of-use schedules, and other bill adjustments are excluded. An effective rate calculated from a total bill may include fixed fees and should not be treated as a marginal usage rate.
Starting values are illustrative, not a market tariff, appliance test, or claim about typical usage. Currency selection changes labels only; no exchange-rate conversion takes place. Small positive costs below one cent are shown as less than 0.01 rather than zero. Calculations run in your browser; this tool does not send or store the inputs.
Worked example
Illustrative inputs: 1,500 W, 4 active hours/day, 30 days, and USD 0.20/kWh (20 US cents/kWh).
1,500 / 1,000 × 4 = 6 kWh per active day.
6 × 30 = 180 kWh.
180 × USD 0.20 = USD 36.00 in variable energy charges.
At the same schedule, the daily cost is USD 1.20. Fixed fees, taxes, and cycling beyond the stated active hours are not included.
Sources
Virginia Cooperative Extension — ENERGY SERIES: Estimating Appliance and Home Electronic Energy Use (publication ID 2901-9014, published February 26, 2020). Supports the watts-to-kWh and energy-cost method; historical example rates and appliance wattages are not calculator defaults. https://www.pubs.ext.vt.edu/2901/2901-9014/2901-9014.html
Validation date
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