What is a kilowatt-hour (kWh)?

A kilowatt-hour is the amount of energy consumed when a 1,000-watt (1 kW) device runs for one hour. It is the standard billing unit on electricity bills.

How do I find the wattage of my appliance?

Check the nameplate label on the back or bottom of the appliance. It usually lists watts (W) or amps (A) and volts (V). If only amps are listed, multiply amps by volts to get watts.

What is the average US electricity rate?

As of 2024 the US average residential rate is about $0.16 per kWh, but it varies widely by state — from roughly $0.09 in Louisiana to over $0.30 in Hawaii. Check your latest bill for the exact rate.

How many kWh does a 1500-watt heater use in 8 hours?

1500 W × 8 h ÷ 1000 = 12 kWh. At $0.16/kWh that costs about $1.92 per day.

Does this account for standby power?

No — this calculator uses a fixed wattage over the entered hours. Standby power (typically 1–5 W for most devices) can add up over time if left plugged in continuously. Run a separate calculation at the standby wattage to factor it in.

Watts to Kilowatt-Hours Converter

Name: Watts to Kilowatt-Hours Converter
Availability: InStock
Author: Nham Vu

Enter watts and usage hours to get kilowatt-hours (kWh) and estimated electricity cost.

Input Values

Power (watts)

Check the appliance nameplate or spec sheet.

Hours of use (per day)

Number of days

Electricity rate ($/kWh, optional)

Leave blank to skip cost estimate. US avg ≈ $0.16/kWh.

Enter watts and hours, then press Calculate.

Common Appliance Wattages

LED bulb 8–15 W

Laptop 30–65 W

Desktop PC 100–300 W

Refrigerator 100–200 W

Microwave 600–1200 W

Space heater 750–1500 W

Air conditioner 1000–3500 W

Clothes dryer 1800–5000 W

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Summary

Enter watts and usage hours to get kilowatt-hours (kWh) and estimated electricity cost.

How it works

Enter the power rating of your appliance in watts (check the label or user manual).
Enter the number of hours the appliance runs per day, or switch to total hours mode.
Optionally enter the number of days and your electricity rate ($/kWh).
The calculator computes kWh = (W × h) ÷ 1000 and multiplies by your rate for cost.
Results update instantly as you type.

Use cases

Estimate the monthly electricity cost of a space heater, air conditioner, or dryer.
Compare energy consumption between two appliances before buying.
Calculate the daily kWh draw of a home server or always-on device.
Size a solar panel system or battery bank for a specific load.
Verify an electricity bill by computing expected usage from wattage and runtime.
Track energy usage of EV chargers, grow lights, or workshop equipment.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu