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How do we use energy?

• To break down and digest food (in our bodies)
• To heat houses and other buildings
• To illuminate lights
• To power televisions, phones, games, cars
• To run computers and appliances

Units of Measure for Energy

In physics, the standard unit of measure for energy is the joule which is abbreviated as J. There are
other units of measure for energy that are used throughout the world including kilowatt-hours,
calories, newton-meters, therms, and foot-pounds.

Law of Conservation of Energy

This law states that energy is never created or destroyed, it is only changed from one state to another
(!!!!!). One example is the chemical energy in food that we turn into kinetic energy when we move.

1.2. Energy production

Energy production and consumption
Primary energy is any extraction of energy products in a useable form from natural sources.
This occurs either when natural sources are exploited (for example, in coal mines, crude oil or
RES facilities).
Transforming energy from one form into another, such as electricity or heat generation in thermal
power plants (where primary energy sources are burned), is not primary production (!!!).
Secondary energy: When we convert primary energy into a transportable form we lead to secondary
energy. For example, when we burn coal in a power plant to produce electricity, electricity is a form of
secondary energy. Secondary energy includes liquid fuels (such as gasoline and diesel – which are
refined oil), electricity, and heat.
Final energy: Once we have transported secondary energy to the consumer, we have final energy.
Final energy is what a consumer buys and receives, such as electricity in their home; heating; or petrol
at the fuel pump. Final energy consumption is the total energy consumed by end users, such as
households, industry and agriculture. It is the energy which reaches the final consumer's door and
excludes that which is used by the energy sector itself.
Useful energy: This is the last step. It is the energy that goes towards the desired output of the end-
use application. For a lightbulb, it’s the amount of light that is produced. For a car, it’s the amount of
kinetic (movement) energy that is produced.

This project has been funded with support from the European Commission. This communication reflects the
views only of the author, and the Commission cannot be held responsible for any use which may be made of the

information contained therein.
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