🔁Convert watts to kilowatt-hours

✓ Tested & verified Updated: Aug 8, 2026 How we calculate this

Watts to kWh converter

Watts

Hours it runs

Supply voltage

Country

Your price per kWh

1.50 kWh = $0.26

At 120 V that appliance draws 12.5 amps.

Running for 24 hours: 36 kWh · $6.12
One kWh at this price: $0.17
What one kWh runs: 0.7 hours of this appliance

Only volts and amps on the plate? Multiply them — 120 V × 12.5 A is 1,500 W. A range like 100–240 V means the appliance accepts either; use the one your country supplies.

Try also

How do you convert watts to kilowatt-hours?

Watts × hours ÷ 1,000 = kilowatt-hours. A 1,500 W heater running one hour uses 1.5 kWh. The same heater for twenty minutes uses 0.5 kWh, and a 100 W lamp for ten hours also uses 1 kWh.

The division by 1,000 is the only step people miss, and it is just the “kilo”: a kilowatt is a thousand watts. The reason bills are in kilowatt-hours rather than watt-hours is scale — a household uses several hundred thousand watt-hours a month, which is an unpleasant number to print.

The other conversion on this page is amps = watts ÷ volts. That is the one that tells you whether an appliance will trip a breaker: 1,500 W on a 120 V circuit is 12.5 amps, which is most of a 15-amp circuit’s continuous capacity. The same appliance on 230 V draws 6.5 amps and barely notices — which is why a European kettle can be 3,000 W and a North American one cannot.

One kilowatt-hour, described six ways. It is the same amount of energy every time.

Appliance	Draw	Time to use 1 kWh
LED bulb	9 W	111 hours
Router	10 W	100 hours
Television	90 W	11 hours
Fridge, while running	150 W	6.7 hours
Gaming PC	450 W	2.2 hours
Space heater	1,500 W	40 minutes
Kettle	2,500 W	24 minutes
Electric shower	9,000 W	6.7 minutes

Read the top and bottom rows together: an LED bulb would have to burn for four and a half days to use what an electric shower gets through in under seven minutes. That ratio, rather than any tariff, is why some appliances matter on a bill and others never will.

Frequently asked questions

What is the difference between a watt and a watt-hour?

A watt is a rate — how fast energy is being used. A watt-hour is an amount — how much has been used. A 100 W bulb uses energy at 100 watts; leave it on for an hour and it has consumed 100 watt-hours, or 0.1 kWh. Bills charge for the amount, not the rate.

How do I convert watts to amps?

Divide by the supply voltage. 1,500 W ÷ 120 V = 12.5 A; the same 1,500 W ÷ 230 V = 6.5 A. For anything with a motor or a power factor below 1 the real current is slightly higher, but for resistive loads like heaters and kettles the simple division is accurate.

My appliance only lists volts and amps. What now?

Multiply them for watts: 230 V × 8 A = 1,840 W. If it lists a voltage range such as 100–240 V, it works on either supply — use the voltage your country actually provides, since the current will differ.

What is the 80% rule?

A circuit should carry no more than 80% of its rated current for a continuous load — anything running three hours or more. A 15-amp, 120 V circuit is 1,800 W on paper and 1,440 W continuously, which is exactly why plug-in heaters stop at 1,500 W and why two of them on one circuit trip it.

Does a kWh cost the same at all times?

Only on a flat tariff. On time-of-use or economy tariffs the same kilowatt-hour can cost two or three times more at 6 pm than at 1 am, and some EV tariffs go lower still overnight. If your bill has more than one rate, put in the one that applies when the appliance actually runs.

How many kWh does a household use?

It varies enormously with heating type and climate — an all-electric home with electric heating can use 12,000 kWh a year while a flat with gas heating uses 2,000. That is why nothing on this site tries to estimate your total bill: it calculates one appliance at a time, which is a question with a real answer.

How we calculate this

Conversions use the definitions: watts × hours ÷ 1,000 = kilowatt-hours, watts ÷ volts = amps, and kilowatt-hours × price = cost. The amp figure assumes a resistive load with a power factor of 1, which is accurate for heaters, kettles and incandescent lighting and slightly understates current for motors and some electronics. Voltage is selectable because it changes the current without changing the energy: an appliance drawing 1,500 W uses 1.5 kWh an hour whether it runs on 120 V or 230 V. The continuous-load figure quoted follows the common code rule of 80% of a circuit’s rating and is a rule of thumb rather than installation guidance.

Worked example

With Watts 1500, Hours it runs 1, Supply voltage 120 V, Country United States (USD), Your price per kWh 0.17, this page works out 1.50 kWh = $0.26. At 120 V that appliance draws 12.5 amps.

Running for 24 hours36 kWh · $6.12
One kWh at this price$0.17
What one kWh runs0.7 hours of this appliance

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