Measuring energy: “how much chocolate do you need to run a washing machine?”
Sources of energy include water, sun and the wind, as well as certain matter, such as food, oil and uranium. Each of these sources is usually measured in different units (calories, litres, kilos, etc.)
In 1849, it was established for certain for the first time that the total amount of energy remains the same both before and after it is converted into another form of energy (taking losses through heat into account, that is). This meant that we could then compare the various forms of energy with one another.
The unit used for measuring energy is the joule. But one joule only represents a tiny amount of energy. As a result, we use other, bigger, units to describe energy (kilojoule, megajoule, kilowatt hours or "ton of oil equivalent").
