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Watts to amps calculator

How many amps does a 1,500 W appliance draw? How many watts on a 30 A circuit? Enter a number: the result shows up right away.

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Watts → ampsExample

Power

7,200W

Voltage

240V

120 V208 V240 V

Current

30A

A 30 A
EV charger

Run my conversion

Convert watts to amps

Enter watts or amps: the other value is calculated right away.

Power

Current

Voltage

7,200 W ÷ 240 V = 30.00 A

In Québec, a house is supplied at 120/240 V. Regular outlets are 120 V; the range, dryer, water heater, baseboards and Level 2 EV charger are 240 V. Some existing buildings are 120/208 V.

Try an example

For a motor or compressor (heat pump, air conditioner, pump), this calculation is an approximation: go by the amperage written on the appliance's nameplate.

Is your 100 amp panel enough? Run the numbers

Quick reference: amps and watts

The power a circuit carries for its rating, at 120 V and 240 V (P = V × I).

15 AAt 120 V1,800 WAt 240 V3,600 W

20 AAt 120 V2,400 WAt 240 V4,800 W

30 AAt 120 V3,600 WAt 240 V7,200 W

40 AAt 120 V4,800 WAt 240 V9,600 W

50 AAt 120 V6,000 WAt 240 V12,000 W

For a continuous load (EV charger, water heater), stay within 80% of the breaker rating: 24 A on a 30 A breaker, for example.

What to know

The formula

For a resistive load (baseboard, water heater, range): P = V × I. To find the amps, divide the watts by the voltage: I = P ÷ V.

Example: a 32 A charger at 240 V draws 32 × 240 = 7,680 W.

120, 240 or 208 V

In Québec, Hydro-Québec supplies houses with single-phase 120/240 V: regular outlets at 120 V; range, dryer, water heater, baseboards and Level 2 charger at 240 V.

Some existing buildings are 120/208 V: a 240 V resistive appliance only delivers about 75% of its power there.

Motors and compressors

For a heat pump, air conditioner or pump, the power factor comes in: P = V × I × PF.

The simple calculation becomes an approximation: the amperage on the appliance's nameplate is what counts.

Is your 100 amp panel enough?

Converting one appliance is the first step. To know whether your service can take an EV charger, a heat pump or a spa, you have to add up the whole house using the Code method.

Run the load calculation

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Frequently asked questions

How many amps is 1,500 watts?

1,500 W at 120 V = 12.5 A. At 240 V = 6.25 A.

How many watts on a 15 amp circuit?

15 A at 120 V = 1,800 W; at 240 V = 3,600 W. For a continuous load, stay within 80% of the breaker rating.

How do you convert amps to watts?

Multiply the amps by the voltage: 30 A × 240 V = 7,200 W.

Is the calculation exact for a heat pump?

No, it's an approximation: a compressor has a power factor below 1. Go by the amperage on the appliance's nameplate.

Is a Québec house 120 V or 240 V?

Both: the supply is single-phase 120/240 V. Small appliances run on 120 V, large ones on 240 V.

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