Power in watts equals amperes times voltage. So, in a direct current, 1 amp at 110 volts equals 110 watts, whereas 1 amp at 220 volts equals 220 watts.

Amp wattage depends on the voltage and on whether it is a direct current or an alternating current. The same appliance can consume more or less watts if it is plugged into a 110-volt current or a 220-volt current. By rule, 220 volts consumes more watts.

In an alternating current, the power factor must also be taken into consideration. The power factor indicates the ratio between real power and apparent power in a circuit.