My electricity bill shows kWh. How do I figure out how much my 900 W space heater costs per month?

900 W = 0.9 kW. If you run it 4 hours per day × 30 days = 120 hours, that's 0.9 × 120 = 108 kWh. At $0.15/kWh that's about $16/month.

I'm adding up appliances for a generator — AC (2400 W), fridge (800 W), lights (400 W). What size generator do I need?

Total: 3,600 W = 3.6 kW running load. The AC and fridge compressors draw extra power at startup. Compare their starting watts with the generator's surge rating.

My solar panels are rated 400 W each. How many do I need for a 10 kW system?

10 kW = 10,000 W. At 400 W per panel, you need 25 panels.

What's the difference between watts and kilowatts in practical terms?

Watts measure instantaneous power draw; kilowatts just scale that by 1,000. A kettle boiling at 2,000 W is using 2 kW right now. The distinction matters mainly for readability — kilowatts are easier to work with for larger appliances.

Watts to Kilowatts Converter

Enter a value to instantly convert between power units.

From

Precision4 dp

1 Watt = 0.001 Kilowatt

Key Formulas

Kilowatt → Horsepower (mech)

hp = kW × 1.34102

Horsepower (mech) → Kilowatt

kW = hp × 0.7457

Watt → Kilowatt

kW = W × 0.001

Kilowatt → Watt

W = kW × 1000

Formula

kW = W ÷ 1000

Electricity bills charge by the kilowatt-hour, but appliance labels show power in watts. When sizing a solar panel system or a home generator, you add up watt ratings of all devices and convert to kilowatts to match the system's output spec. A 2,500 W central air conditioner becomes 2.5 kW — making it easier to see how many hours you can run it on a 10 kWh battery bank.

Source: NIST SP 811, Table B.8

Reviewed by the Convert Calc editorial team · Last reviewed: 2026-10-06 · see our methodology

Frequently Asked Questions

Real-World Examples

A 100 W incandescent bulb draws 0.1 kW. Running it 10 hours uses 1 kWh. At $0.15 per kWh, that costs $0.15.

100 W = 0.1 kW

A 1200 W microwave runs at 1.2 kW; a 10-minute use takes 0.2 kWh, about 3 cents at 15 cents per kWh.

1200 W = 1.2 kW

A 3500 W clothes dryer draws 3.5 kW. Include it when sizing a backup generator.

3500 W = 3.5 kW

A 7200 W Level 2 EV charger draws 7.2 kW, about 72 kWh over 10 hours. Follow the charger's installation manual for the circuit rating.

7200 W = 7.2 kW

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