How do I convert watts to kWh?

Multiply watts by hours and divide by 1,000.

How is appliance electricity cost calculated?

Multiply energy use in kWh by the electricity rate per kWh.

Will this match my electricity bill exactly?

Not always. Taxes, fixed charges, tiered rates and cycling appliances can change the bill.

Developer ToolUtility Tool

Electricity Cost Calculator

Estimate appliance energy use and daily, monthly or yearly electricity cost. Enter your values and see the result instantly.

Watts to kWhMonthly estimateMultiple appliances

Quick and private: Only the essential fields are shown. Your values are calculated in this browser and are not stored in our database.

Enter details

Electricity Cost Calculator

Appliance power (watts)Hours used per dayBilling period (days)Electricity price per kWh

Calculate appliance electricity use and running cost

Estimate what a heater, air conditioner, computer, fan, light or other appliance costs to run. Enter rated watts, hours used each day, billing days and the usage price from your electricity bill. The result shows energy consumption and scales the same schedule to daily, 30-day and annual estimates.

Watts to kWh formula

Energy (kWh) = watts × hours × days ÷ 1,000. Electricity usage cost = kWh × electricity rate. For several identical appliances, wattage use is multiplied by quantity.

Example monthly appliance cost

A 1,000-watt appliance running four hours daily for 30 days uses 120 kWh. At $0.15 per kWh, its estimated usage cost is $18 for that period.

Why the estimate may differ from a bill

Some appliances cycle or vary their power draw. Electricity bills may also include fixed charges, taxes, time-of-use pricing and tiered rates. A plug-in energy meter or appliance kWh report can provide a better input than maximum label wattage.

Frequently asked questions

What is a kilowatt-hour?+

One kWh is 1,000 watts of power used for one hour and is a common electricity billing unit.

How do I calculate appliance kWh usage?+

Multiply watts by operating hours and number of days, then divide by 1,000.

How do I calculate electricity cost?+

Multiply total energy consumption in kWh by the price charged per kWh.

Can I calculate several identical appliances?+

Yes. Open Options and change Quantity to include multiple devices with the same wattage and schedule.

Does standby power count?+

Yes. Add standby watts and inactive daily hours in Options when the device continues drawing power.

Why might label wattage be inaccurate for monthly cost?+

Some appliances cycle on and off or vary power. A measured kWh reading can be more representative than maximum label wattage.

Does this include fixed bill charges and taxes?+

No. The estimate covers usage cost from the entered rate; fixed fees, taxes and tiered tariffs may be additional.

Can I compare an old appliance with an efficient one?+

Run both wattage scenarios using the same hours, days and rate, then compare their monthly and annual results.

Developer newsletter

Stay ahead with new tools

Get practical developer guides, new tools, and workflow improvements without inbox noise.