Negative consumption numbers with solar and discrepancies with energy company

#1

Looked around and couldn’t see an immediate answer to my questions. First off, I have a “MyEnlighten” monitor that is tracking my solar production, and now I also have a Sense monitor tracking my consumption. It has only been up and running for a couple of days but I have two questions:

  1. Is it normal to have negative consumption values in the day when solar is producing more that I am consuming?

  2. Is there something in my set up that is messing up the grid consumption numbers? When I take out the hours in one day where I had negative consumption numbers (when I was using practically no energy from the grid) and add the total consumption of the hours where I was using from the grid, it is less than half what the energy company says I used. Why?

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#2

Help us understand your setup. You have your Enlighten app only monitoring solar production, and your Sense only monitoring usage on your house mains ? I ask, because apps can monitor both with the correct options.

If you are using Sense without Sense Solar, on a house with a solar backfeed, the Sense output will be showing net usage, not total house usage. In that case, it would be normal to see negative instantaneous consumption number when your solar is producing more than your device in the house are using.

As for differences with your utility, I would compare the hour by hour Sense exported data with exported hourly power company data (if available) to pinpoint the issue.

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#3

Yes, my Enlighten monitor is not the type that can monitor consumption, and I have the regular, non-solar Sense monitor, so it is not measuring solar supply.

So, when you say net usage, this means 1) when I am using less energy than I am producing the Sense will show how much is being fed into the grid, and 2) when I am not producing more than I am consuming, the Sense will show total usage, regardless if this is coming from the panels or the grid? Or is it only showing what is being used from the grid?

Next, unfortunately I cannot get hourly data from my company. But when I took out the five hours where my energy usage was net negative and I only added the hours where I was in positive territory I end up with 12 Kw. But the energy company has me at just over 20 kw. I am aware that in some of the net negative hours there couple of blips where energy went over net 0, but that couldn’t be enough to account for 8kw. I suppose I could look at the meter and compare to Sense, but I am just wondering if the solar is somehow skewing the numbers?

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#4

A few thoughts.

  • Net Usage is the house Total Usage minus Solar Production at a moment in time. When Solar Production is smaller than Total Usage, Net Usage is positive, when Solar is larger, Net Usage goes negative. Net Usage is what is coming from the grid, when positive and what is going back into the grid from your solar, when negative.
  • Cumulative Net Usage is the summation of Net Usage over time, the thing that your power company should be metering if you have a Net Meter (one that “spins” backwards) as well as forwards. Hopefully, the power company installed a new net meter when you put in your solar PV system.
  • Sense should be showing your Net Usage (what’s coming/going from the grid) in the Power Meter display, and cumulative Net Usage in the Usage summaries for different time periods, if Sense is connected up in the normal way (on your house mains).

Did you get a new NEMS (net meter) installed when you added solar ? If not, that would account for the hefty difference between Sense cumulative net usage and your utility.

ps: It might be worth the 50$ to add solar to your Sense, if it is physically possible, just to see all your electric use data in one place.

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#5

Thanks for this, it does clarify things.

Regarding the energy company, they did install a new meter, but we don’t do net metering, instead we get an “energy avoidance” credit via “bi-directional” metering on the next bill for any energy we put into the grid.

So, on this one given day I used 10kw of grid energy, 10kw of solar, and I put 10kw into the grid from solar. But the energy company has my usage at 20kw. I am not sure if they will amend this when its time for the bill, but it looks like they are including something from the solar in their usage calculation. I will have to get in touch with them next and see what they say.

Thanks for the help.

H.

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#6

Just to bring this full circle. I did get in touch with the energy company - Georgia Power - and they confirmed that they had not yet installed a new meter. It’s been 2 weeks! So they are taking their time while they conveniently charge me for the solar energy I am producing . . . Somehow I’m not surprised.

H.

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#7

Thanks for sharing… Very good reason for seeing excess energy charges ! This one is worthy of “Share Your Sense Stories”.

https://community.sense.com/c/sense-stories

I busted my power company :slight_smile:

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