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We went on vacation for two weeks recently and I noticed that our PG&E bill had some unusual behavior.

  • Our overall bill wasn't that much lower than it was when we were home.
  • Different days had very different amounts of energy use. One day (63 degrees average temperature) had 5 kWh of energy usage and a few days later (65 degrees average temperature) PG&E reported 15 kWh of energy usage.

What could cause such fluctuations in our electricity use? We closed the windows and blinds and unplugged most disposable electronics except the TV (which was turned off), refrigerator and a small Coway air purifier (left on by accident). The refrigerator was installed within the last five years.

A smart home app sends alerts any time the doors open or close, and it did not fire for the entire vacation, so there's no chance family members or kids were secretly home.

We have a gas heater, no A/C and the we set the thermostat to "eco mode" = 50 degrees = while we were gone.

edit Here's a photo from the low energy day, 5kWh of energy use:

Hour by hour chart of low energy usage

And high energy usage - note the different scale on left hand side.

hour by hour chart of high usage

No one was in the house on either of these days.

  • 1
    maybe somebody is pirating your power – jsotola Sep 1 at 6:01
  • Perhaps the fridge had to work harder on the warmer day? Is it a small unit or a barn sized one with cold water fountain, beer and slushies all built-in? – Solar Mike Sep 1 at 6:19
  • You have a smart meter, and the energy usage numbers aren't estimates, right? Also, since your heat is electric, there shouldn't be any correlation between the temperature and the power usage. – user3757614 Sep 1 at 6:19
  • I have a meter provided by PG&E with a digital readout of the power consumption. I am basing the energy usage numbers based on a dashboard provided by opower.com (available through the PG&E dashboard) It's possible the numbers are estimates though I believe PG&E uses the same ones to compute the bill. Not sure how you define "small unit", it's a side by side refrigerator + freezer that's pretty common in an American household. It's possible someone is pirating my power but very unlikely based on the configuration of our house. – Kevin Burke Sep 1 at 6:33
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    Average temperature doesn't mean much. What were the highs and lows? Also, what appliances remained hooked up that could draw 400W or more? – Harper Sep 1 at 8:09
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Do you have any electrical convenience outlets on your house ? While your home's inside is secure, what about the outside ?

I would look into the possibility of the above.

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You say, “Energy Use”, but really it’s your electrical use you’re concerned about.

The item that uses the most energy in any home is the heating/cooling. However, you indicate that you have gas heat and no cooling. Therefore, that would not affect your electric bill whether you’re on vacation or not.

The second most energy user is usually the water heater...which is affected by laundry, bathing, dishes, etc. Not doing these activities could significantly reduce your electric bill.

Cooking is also something that uses a significant amount of electricity...oven, toaster, crockpot, etc. If you don’t use these a lot normally, then you would not see much change when on vacation.

Last is lights, chargers, etc. These use minor amounts of electricity, so no use when you’re on vacation would not reduce your total cost by much...

I would focus on checking the water heater. If it’s cycling on and off it could affect you electric bill the most.

It’s curios how the utility knows how much energy you used each day...did you get a printout of you daily use? Is this normal getting this from your utility?

I’d expect my electricity use to be fairly consistent day-to-day when no one is in the house for two weeks. (Do you suspect teenagers giving your security access code to friends and neighbors?) Is there anything on a timer, like pool heater, sauna, roomba, etc.

  • Edited the question to mention electricity specifically. – Kevin Burke Sep 1 at 6:36
  • We have a digital meter and a dashboard through opower.com that reports the daily usage rounded to the nearest kWh. It's possible it's inaccurate. – Kevin Burke Sep 1 at 6:37
  • No teenagers or family, at least, if anyone was in the house they did not go in through any of the doors, otherwise our contact sensors on the doors would have notified us that someone opened or closed them. – Kevin Burke Sep 1 at 6:38
  • Could the water heater be involved at all in powering the operation of the fridge? – Kevin Burke Sep 1 at 6:42
  • @KevinBurke Not at all. The problem with this question is that we have no idea what your appliances are. Therefore any possible answer is going to involve wild reaches of guesswork. For instance my best guess is your dual-1080 gaming PC got hacked and was used to mine bitcoin, because that would explain 400W 24x7. Because this is so unanswerable, I'm considering voting to close. – Harper Sep 1 at 9:17
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Check to see that each day is separately accounted for during your vacation. Dashboards read smart meters once a day, usually around midnight and compare that reading to the day before to get the daily usage. If, for some reason, they don't read it on a particular day, which does happen due to computer problems, etc., the next day's reading will appear to be twice as much. Sometimes they will go back and correct it but not always.

  • I've worked directly with smart meters, created dashboards, etc. Typically a smart meter will produce a lot of data and have a decent memory (days or even weeks of 15-minute data), so a problem transmitting data will result in a delay in the dashboard, but if designed properly will not result in any gaps or double-ups. Of course, things are not always designed properly... – manassehkatz Sep 1 at 14:55
  • Thanks for the suggestion... I guess if this were to happen I would expect a small day to be followed by a big day and I don't really see that in the data. – Kevin Burke Sep 1 at 15:52

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