How does my electric company know what exactly is using the electricity?


Looking at my electric bill, there’s a section saying “this percent came from [ex: Air conditioner, major appliances (fridge, oven), etc]”. How do they know that?

In: 383

Every day at your AC kicks on at random times, but when it does, there is a sudden spike of power use and its about the same power amount every time, then the spike drop off as the AC turns off after a certain amount of time. The amount of time is nearly the same since the AC kicks on at the same temp and kicks off at the same temp and the pow draw is nearly the same.

Very easy to see these power jumps.


Some of it may be reasonable guesses (your base usage on days you wouldn’t need AC vs the spike on hot days).

Some of it may be based on load monitoring and what that tells them. e.g. The compressor coil for your fridge and AC are going to have identifiable start up characteristics, and then the increased draw of them can be extrapolated vs the background levels of things like lighting that’s relatively static. They may not be able to tell a toaster from a curling iron, but with a clever enough meter they can probably tell a blow dryer from a toaster based on the motor.

Utilities have used (and use) both methods, as well as smart appliances that “talk back” to the grid for those sorts of things.

The smart appliances are usually “big” appliances like your AC or water heater that you’ve agreed to letting them turn them down/off at periods of peak demand.

They guess. The look at how much power you used, and look at weather records, and they guess how much was used by each thing.

We have two standalone chest freezers. The power company keeps suggesting we get rid of our garage fridge, so they probably are looking at compressor load.

It’s mostly an educated guess. If you go into your account on their website they very likely have a section for you to fill out with how many people live in the house, what appliances you have, how many phones and computers you have, how much square footage you have, etc.

The meter outside your house constantly collects data and sends it back to the power company, which analyzes that data both in real time and historically for various purposes, and when they combine that with what you tell them *and* what they already know about typical usage for various appliances and items, they can get a pretty accurate estimate.