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?
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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.
Depends.
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.
I can’t say that o have seen that specific detail on my bill ever here on Australia
Do you have a smart meter installed? It could be that those appliances are connected seperately to the meter and the smart meter can report those seperately? Or the smart meter is making an estimate based on the load spikes or decreases
https://www.imeche.org/news/news-article/smart-meter-tracks-power-consumption-of-individual-devices
https://www.mihagrabner.com/post/how-to-recognize-appliances-from-smart-meter-data-using-ai
They may also be guessing based on weather, average household patterns in the area etc
All electric motors have a locked rotor amperage printed on the information plate. This is the amperage it draws when power is going to the windings (the sitty still part) but the rotor isn’t moving (the spinny part) off the rotor were rusted in place, the motor would draw locked rotor from the time power was applied until it was shut off (with larger motors that would be when the breaker trips) the compressors in most residential air conditioning systems have locked rotor amperages easily around 100 amps. Refrigerators and such, can be around 30 to 50. When you turn it on, the rotor isn’t moving. The electric field produced in the windings has to get it moving and that happens very fast, but for a split second it draws locked rotor amps. Then it will run at around 10-20 amps until it shuts off. Your furnace blower will draw 40-50 or so locked rotor amps as well for that split second. Then it will run at around 8 amps until done. Fan motors in refrigerators will draw a comparably small locked rotor amperage (maybe 10) so when they see a big spike (home a/c starting) of around 150 amps, followed by a 20 minute period of around 25 amps, they know your air conditioner is running, because virtually nothing else anyone has at their home would share that profile. A spike of around 60 amps, followed by a 20 minute draw of around 10 amps, tells them you have a refrigerator or freezer running for the same reason. The commenter who’s being told to get rid of their garage fridge, it would be because they see that profile either at two different times at intervals that don’t make sense for one appliance, or because they see it happen again while the first one is already running. For other appliances, if they aren’t cooling they’re probably heating. Toasters, electric ovens, etc draw high amperage continuously but have no spike when they start. Dishwasher’s and such draw lower amps but also have no spike. But all of those won’t be turned on for hours at a time like lights or tv’s. So they get labeled as “other appliances”
They don’t know. They can make an educated guess.
There are technologies being developed that recognize “signatures” of certain kinds. The last study I saw was trying to differentiate between different types of incipient fault conditions. But to my knowledge, no residential meter, smart or otherwise, has the capability to differentiate loads. And even if they could, I don’t think the utility would invest the kind of cost that would be associated with it.
https://core.ac.uk/download/pdf/4270075.pdf
Example – Guy is arrested for pulling amps between 2am and 4am by FBI. They suspected he is growing illegally because the plants require water and light at specific amps. Reality, he works third shift and joined an online wood-working class where he uses a table saw and power equipment late through the night in his basement. Case dismissed.
Each appliance draws amps differently past the meter on the side of the house. Refrigerator compressor turns on? Maybe 10 amps with a specific startup draw of 12 amps.
My gas company does the same thing, including telling me how much is from a gas stove that doesn’t exist.
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