Electricity Cost Calculator

Estimate a device's energy charge

Enter rated or measured watts per device, device count, daily run time, number of days, and an all-in price per kilowatt-hour when available. The result shows energy use and a simple usage cost.

Watts, hours, and kilowatt-hours

Watts describe power at a moment. Energy accumulates over time. Multiply watts by quantity and hours, then divide by 1,000 to get kilowatt-hours. Multiply kilowatt-hours by price per kWh to estimate the energy charge.

Worked example

Two 60-watt lamps used five hours per day draw 600 watt-hours, or 0.6 kWh daily. Over 30 days they use 18 kWh. At $0.15 per kWh, the estimated usage cost is $2.70, averaging $0.09 per day.

Use measured power when possible

Nameplate wattage may be a maximum or nominal value. Refrigerators, air conditioners, heaters, computers, chargers, pumps, and motor-driven equipment can cycle or vary their draw. A suitable plug-in meter or trusted device data gives a better average for compatible loads.

Choose the right electricity price

A bill's total divided by billed kWh can provide a rough all-in average, but fixed fees do not scale with one appliance. Time-of-use rates, tiers, demand charges, taxes, credits, fuel adjustments, and net metering can make marginal cost different from a single rate.

Standby and duty cycles

Enter average watts across the hours counted, or estimate active and standby modes separately and add their energy. Do not enter 24 active hours for a device that cycles unless its entered wattage already represents the daily average.

Limitations and privacy

This is a straight-line estimate. It does not read a meter, forecast utility rates, calculate battery losses, power factor, demand, solar production, carbon impact, or electrical safety. It is not a wiring or circuit-sizing tool. Inputs stay in the browser.

Electricity Cost FAQ

Can I use amperes instead of watts?

No. Convert or measure power first; voltage and power factor can matter.

Should I include fixed monthly fees?

Usually not when estimating the added cost of one device, because fixed fees may not change with use.

Does rated wattage equal actual draw?

Not always. Variable and cycling equipment benefits from measurement.