Energy Concepts: Power versus Energy

It is often tempting to use the words “power” and “energy” interchangeably. However, they are not, in fact, synonyms. In this blog post, we are going to share a brief explanation of the difference between the two. 

Fundamentally, power refers to a rate while energy refers to an amount. Power is a measure of energy flow. It identifies speed – the rate of energy delivery or how quickly energy is used. Power is measured in units such as watts, Btuh, horsepower, Bbl/day, calories/day, or ergs/sec. Energy, meanwhile, refers to a total amount produced, used, or delivered. It is a measure of quantity. Energy is measured in units such as watt-hours, mmBtu, therms, barrels, or joules.

Here are some real-world examples:

  • A 60 watt (power) lightbulb that runs for 12 hours uses 720 watt-hours (energy) of electricity.
  • A 200 watt (power) street lamp that runs for 12 hours uses 2400 watt-hours (energy) of electricity.
  • A 1000 megawatt (power) power plant that operates for 30 days produces 720,000 megawatt-hours (energy) of electricity.

The graphs below further illustrate the point. The blue line on the top graph shows the rate at which electricity is being used (i.e., power). The graph on the bottom shows the total amount of electricity consumed (i.e., energy).

Stay tuned for future blog posts in which we will present additional energy concepts.

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