Explain like I am five how does the electric company make the amount of power you use and not just turn on endless power. How does the power they make go to you and the amount is known?
The amount they make is carefully balanced by the generators (and their control systems). The generator is a physical spinning thing. It wants to spin at a fixed speed. If the supplier makes more energy than is used that extra energy goes in to spinning the generator faster, they detect this and dial back a little. Similarly if there isn’t enough the generator slows down, this is detected and more energy is put in.
You can think of the energy going in as just throwing more fuel in the fire to make it hotter.
As for the amount you use, that’s very easy to measure at the cables that come in to your house. Measure the current and you can work out energy easily and accurately.
As for billing you, that’s slightly different! It’s almost impossible to know who is actually giving you your energy. Think of it like a big swimming pool: lots of suppliers turn on the taps to fill up the pool with energy. Once it’s in the pool it’s impossible to tell apart different energy sources because they’re all mixed. You take energy out the bottom of the pool, once it’s all mixed.
In reality we just agree to pay a particular supplier for energy. Some areas don’t have a choice and must pay a single person, others may have a choice and can choose the cheapest. Note that they all charge different rates & methods so what is cheapest for you may not be cheapest for your neighbour.
Electricity is made by spinning a magnet, connected to wires, connected to your house.
Suppose you have a magnet connected to wires, geared into an exercise bike’s mechanism and then pedal the bike. The other ends of the wires are connected to a TV.
When you turn on the TV, it acts like a brake on the spinning magnet. So if you’re riding on the bike and someone switches on a TV, you’ll suddenly feel like you’re riding uphill. You have to pedal with more oomph, or you will slow down.
Electrical generators constantly check whether they start running slow (or fast), and adjust to burn more (or less) fuel. If all the generators are burning near their minimum (or maximum) fuel, they tell Central Control, who tells some generators to start up (or shut down).
Nowadays we use computers for the measuring and adjusting. But originally they used various [ingenious mechanisms](https://en.wikipedia.org/wiki/Centrifugal_governor) for controlling steam power.
If the power they are making is not being used up, their generators experience less load (they become easier to spin) and they start to speed up above the 50/60Hz setpoint. They monitor this and lower the energy input to the turbine spinning the generator. The opposite happens when they are making too little power. Note that this frequency shifting affects all generators connected to the same grid, so it might not need every power plant to change up their output to balance it. They communicate with each other and the plant(s) which can most economically ramp up/down at the moment to balance the system do so.