Power
How quickly energy is transferred or used.
A constant 2 kW rate is shown as a horizontal line; energy depends on how long that rate lasts.
Power is the rate of energy transfer. Real electrical power is measured in watts; kilowatts and megawatts are common units for equipment and grid-scale resources.
A rate, not an accumulated amount
A watt is one joule per second. Power tells you the rate at which energy is transferred at a moment, or averaged over a specified interval. Grid-scale power is often expressed in MW.
For a constant load, energy is power multiplied by elapsed time. When power changes, the total energy is the area under its power-versus-time curve. A high power rating does not by itself tell you an annual energy total.
Why it matters
Separating power from energy avoids confusing the size of a generator, cable, or battery inverter with the amount of electricity delivered over time.