Energy return on energy invested

When you want to do something, like play with your toys or run around outside, you need energy in your body to do it. Energy is what gives you the power to do things.

Similarly, when grown-ups want to do something, like drive cars or use electricity in their homes, they also need energy. But, the energy they use usually comes from sources like coal, oil, and gas.

The problem with those sources is that they don't just give us energy automatically. To get the energy out of them, we need to do work to extract it-- like digging up coal or drilling for oil, which takes energy itself.

The Energy Return on Energy Invested (EROEI, for short) is like a scorecard for how much energy we get out for the energy we put in. It's all about measuring how much energy we get from a source, like coal, compared to how much energy we had to use to get it.

For example, imagine you had a toy car that was powered by a battery. If you used a lot of energy to build the battery in the first place but only got a little bit of energy out of it when using the car, then the EROEI would be low.

But, if you had a toy car that was powered by a solar panel, and it gave you lots of energy but you only had to use a little bit of energy setting it up, then the EROEI would be high.

So, when grown-ups think about where to get their energy from, they want to try and find sources with a high EROEI. That way, they can get a lot of energy without using too much themselves.

Overall, EROEI helps people to understand the efficiency of different energy sources and helps to guide decisions about which ones are best to use.