Power versus Energy
- Power and Energy are frequently used interchangeably.
- They are not the same. This page simply explains the difference.
Example of power v. energy with lightbulbs
Simplified Example of Energy Use in a Home
Assume a simplified scenario of Home Power Usage:
How it looks on a graph:
How it calulates:
11 hours x 500 W = 5500 Wh = 5.5 kWh
2 hours x 2000 W = 4000 Wh = 4.0 kWh
6 hours x 3000 W = 18000 Wh = 18.0 kWh
2 hours x 4000 W = 8000 Wh = 8.0 kWh
2 hours x 5000 W = 10000 Wh = 10.0 kWh
1 hour x 6000 W = 6000 Wh = 6.0 kWh
Total Energy Usage for 24 hours = 51.5 kWh
Why do we need to know this?
- Because you need to distinguish between intermittent sources of power and continuous sources.
- Intermittent sources such as solar or wind provide power only when the sun shines or when the wind blows.
- But claims typically do not make a distinction. Example: "... a 92 megawatt solar thermal plant could produce enough electricity to power 74,000 homes... (Reference 5)
- This may be true at noon on a sunny day, but this source will power exactly zero homes at night.
- Thus without some kind of energy storage, intermittent power sources do not provide an energy solution.
We have Power Plants, but we have an Energy Policy. It is essential to understand this distinction in shaping policy decisions.
Notes:
- Energy Storage will be addresses inin this website in the future.