How do I calculate the power consumption of an electrical product?

The key formula to remember is this:

Watts = Amps x Volts

By modifying the formula you can use any two of the items above to generate the value
To calculate Volts:

Volts = Watts / Amps

To calculate Amps:

Amps = Watts / Volts
So let’s look at some everyday examples:

1) To calculate the biggest electric fire that can be run on a 13 amp fused plug in the UK:

Mains voltage in the UK is 230v so Watts = 13 x 230 = 2990 watts or just under 3kW

2) To calculate how many amps an in-car cool box will consume and determine the correct power needed for a mains to 12 volt converter:

A typical cool box is around 70 watts, running at 12 volts. Therefore Amps = 70 / 12 = 5.8333 recurring, or just under six amps.

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