Power is measured in different ways depending on what type of power is being used. Electrical power is measured by the watt or joule. Other measurements of power include ergs per second, horsepower, metric horsepower and foot-pounds.
The mathematical formula for power is Power = Energy/Time. Energy can then be measured by using the formula of Energy = Power x Time.
Power and energy are very similar but are not the same thing. Power is the rate at which energy is delivered. Amps and voltage are not measurements of power. Amps measure current, while voltage measures how much electrical energy is delivered.