When we talk about where energy is from, it helps to know if that energy is directly from a source, or created from another source. 

Primary vs. secondary sources

Primary sources of energy are found in nature. They include coal, natural gas, water and wind. The Sun is the original energy source for all of these things. 

There is one primary source of energy that doesn’t rely on the sun. It’s heat energy from the centre of the Earth, which rises up through vents in the sea. Down there, giant tube worms and clams rely on this energy to survive.

Secondary sources of energy are produced from primary sources. An example of this is when we use coal to make electricity. Coal is the Primary source and electricity is the Secondary source. 

Electricity can come from both renewable and non-renewable primary sources. In Australia, the main way we generate electricity is in power plants that burn coal, a non-renewable fossil fuel. 

What watt?

Measuring electricity use

Electricity is measured in watts (W), with the amount of electricity used over an hour in watt-hours (Wh).

Understanding different
watt (W) ratings

A duller light bulb might have a rating of 40W and a brighter bulb a rating of 100W. Over an hour, the 40W light bulb uses 40Wh of electricity; while the 100W light bulb uses 100Wh of electricity.

It all adds up

Your electricity bill adds up all the watt-hours of electricity used in your home over a set period. So, the more appliances you use, and the more energy-hungry these appliances are, the higher your bill. Electricity bills give the total number of kilowatt hours (kWh) of electricity used by a household over several months.

Ways to save

Check the Energy Rating Label on appliances in your home. The Energy Rating Label, or ERL, lets you compare similar appliances. The more stars, the more efficient. It also provides the energy consumption in kilowatt-hours (kWh) per year. When it’s time to replace your dishwasher, for example, buy a new one with a higher star rating to reduce your electricity bill and be kinder to the environment.

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A Watt Is A Measure Of Energy Flow - We Use Energy To Generate Power

Energy transformations


Energy transforms or changes form all the time. Think about your typical light bulb; the electricity turns on the light which then changes to heat energy very quickly. This is energy transformation.


Chemical energy is another type of energy that we use, and constantly transform. It’s found in all the food we eat, and our bodies transform it to enable us to grow and move. It’s also found in the fuels we use.


Even things that don’t move have energy. A pencil lying on a desk has potential energy or stored energy. This changes to kinetic energy or movement energy when you push the pencil off the desk.


Some kinds of energy are harder to detect, like X-rays or UV radiation. But these types are still used all the time. Think of the sun – it’s powered by nuclear energy, and without it, life as we know it wouldn’t exist!

Energy Transformation Examples

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Wrap up


Primary sources of energy are found in nature, and most primary sources first got their energy from the Sun. They can be renewable or non-renewable.


Secondary sources of energy are those that we have converted from primary sources, so we can use them in daily life. Electricity is a great example.


Electricity is measured in watt-hours (Wh), and different household appliances use different amounts. Energy Rating labels on appliances spell this out.


When we use energy, we’re transforming it from one form to another. Other than a light bulb, what other examples can you find where one energy turns into another?