Update: I am actually searching for really simple, intuitive ways to explain it. I have a background in engineering, but am struggling to explain why we “pay for kwh”, and not kw (on our electricity bill) to someone who doesn’t. I have tried in many ways but maybe I’m not giving the right examples or making the right comparisons. I am really searchig for a way to ELI5.
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A kilowatt is 1,000 joules per second. A joule is just a standard unit of energy. If you express kilowatt as the fraction 1,000 joules / 1 second, then multiply that by 1 hour (3,600 seconds), you find that the seconds unit cancels out. One kWh is the same thing as saying 3,600,000 joules of energy.
Electricity is measured in watts, because it is really easy to use when working with electricity. Watts = volts * amps. If you know your voltage and amperage, you know the watts. If you know the watts and how long you pulled those watts, you know how much energy you used.
For instance (making all of these numbers up). If you have an electric motor that operates at 9 volts and draws 2 amps, you know you need 9 volts * 2 amps = 18 watts to power the motor. If you need a battery to power the motor for 3 hours, then the battery must have a capacity of at least 18 watts * 3 hours = 54 watt hours.
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