The rate and the total
Power is the rate at which energy is transferred or used. A watt is a unit of power; a kilowatt is 1,000 watts. A kilowatt-hour is a unit of energy. The U.S. Energy Information Administration uses these distinctions when explaining electricity measurement.
Add the time
A device drawing a constant 100 watts for two hours uses 200 watt-hours, or 0.2 kilowatt-hours. That example assumes a steady draw. Real devices can vary with load, settings, and operating conditions, so a rated power figure may not describe an entire session.
Compare like with like
When reading about a battery, look for an energy figure as well as the power it can deliver. For equipment, check whether a number describes peak output, continuous operation, or a measured average. The units help reveal which question the figure answers.
Keep the boundary consistent
A useful comparison uses the same time period and measurement boundary. Does a result include supporting equipment? Was it measured at the device or elsewhere? Those details make a small number much more informative.
What does the evidence show—and what still needs to be tested?
Sources & further reading
U.S. Energy Information Administration · Measuring electricity ↗An original educational explainer, not a report of hands-on testing. Sources provide background; they do not endorse Nanoirev.
