That's because watts = volts x amps So if you look on the back of an electrical device (or on a lightbulb) and it says 1200 watts, and you live in the U.S. or Canada where your house has 120 volts, then: 1200 watts = 120 volts x 10 amps Houses in other parts of the world have electricity that is 240 volts.read more >>