The world is growing. Not just by the population but in technology as well. There was candles back in the day now most of our devices and 99% of whatever we use consumes electricity. Electric meters are those things that usually are set by the service provider and it measures how much we use per month/year, depending on our choice how we pay for it. Yes, this is the main source for the provider company on billing. Most cases it is measured by the amount of kilowatt hours (kWh) at domestic use. And that amount can be much less if we are watching what we use and how, switching things off when we aren't using them. With some “smart devices” you also can get the usage information for any specific thing. This is good to know for example, the microwave oven takes up a multiplied amount than usual if something is wrong with it and needs to be replaced.