Tutorial Article by Robert Hargraves
“Energy is the ability to do work. Power is the rate of energy flow. Electric power is transmitted by electricity flowing through wires. It’s measured in watts or its millennial multiples: kW, MW, GW. Don’t mix up energy (measured in kWh) with power (measured in watts) as many reporters do.
Energy is power times time. One watt of power flowing for one second delivers one watt-second = one joule of energy; J = W * s. One ampere of electron current flowing across a voltage drop of 1 volt transmits one watt of power; W = A * V. A kilowatt-hour (kWh) is the energy of 1000 watts flowing for 3600 seconds, 3.6 * 10**6 joules. One kWh costs on average, about 5 cents to generate and 15 cents delivered to a home.”