The Difference between Energy and Power: Do Not Confuse
"Work" Preface: A joule is used as either a unit of energy or a unit of work. Technically, energy is the ability to do work (effort or input for potential work) while work is the measured effect of applied energy (accomplishment or result or output); directional mechanical work = force * distance and the motively similar thermodynamic work = energy transferred. Your electric bill measures what reached your meter (the work/accomplishment from the power company's view), not how much benefit you wrung out of it.
- energy = work (technically, the ability to do work)
- power = work rate (energy per time)
- joule (J) = energy (work)
- watt (W) = power (rate of work, energy per time)
- watt-hour (Wh) = energy (work)
- energy = J
- power = J/s
The trick is that the word "watt" includes a built-in time component:
- 1 watt = 1 joule per second (Jps or J/s)
- 1,000 watts = 1,000 joules per second
- 12,000 joules PER SECOND = 12,000 watts = 12 kilowatts
- 1 watt-hour (Wh) = 1 joule per second for an hour (3,600 seconds) = 3,600 joules (energy)
- 1kW=1,000W (power)
- 1kWh=1,000Wh (energy)
If you did a "speed" of 1kW for 12 hours, then you totaled 12kWh.
If you did a "speed" of 2kW for 6 hours, then you totaled 12kWh.
A final definition will allow you to make sense of many consumer electronic labels:
- watts (W) = volts (V) * amperes (A)
- W * h = Wh
- 2W * 3h = 6Wh
- J/s = 1 joule divided by 1 second