Tesla app usage doesn't match SCE bill

[llamafilm]

I bought a house with Tesla solar panels (PPA) a few months ago, and now that summer temps are heating up I'm taking a closer look at the bill. It seems like the Tesla app is grossly under-reporting my usage. Here are some screenshots from one day, but it seems to be a similar issue every day. I do not have a home battery. I charged my car overnight, so the high usage between 12-7am makes sense. The SCE bill shows that I used 77 kWh this day, while the Tesla app shows I used 34 kWh. Am I reading this wrong?

The Tesla app lets you export daily usage data in CSV format. So I took this and lined up the monthly start/end dates to match my SCE bill. With Tesla's numbers, I subtracted the total "From Grid kWh" from the "To Grid kWh" and it shows I produced a net surplus of 108kWh for the month of June. But according to SCE, I actually consumed a net positive of 335kWh. So Tesla's data appears to be off by 443kWh, in other words a 132% error!

 

[hayhayday]

The difference seems to be aprox the amount of night time usage, is your ev charger monitored by teslas cts?

 

[llamafilm]

It should be! The solar panels are connected to a Solivia inverter in the main breaker panel. The system came with a Powerblaster CT around the two hot wires coming in from the grid. Plus I only took delivery of the car 1 week ago, so that would not have any effect on my data from June.

 

[dareed1]

If I'm reading the data correctly, there is a major discrepancy in the July 4 data from 12AM through 7AM. The SCE bill shows about 63kWh of usage while the Tesla app reports something like 7kWh. Later in the day, the two data sets roughly correlate. Either SCE or Tesla are confused about the date or time of day, or (more likely) the car charger isn't actually monitored in the Tesla app.

 

[MCNE]

I bought a house with Tesla solar panels (PPA) a few months ago, and now that summer temps are heating up I'm taking a closer look at the bill. It seems like the Tesla app is grossly under-reporting my usage. Here are some screenshots from one day, but it seems to be a similar issue every day. I do not have a home battery. I charged my car overnight, so the high usage between 12-7am makes sense. The SCE bill shows that I used 77 kWh this day, while the Tesla app shows I used 34 kWh. Am I reading this wrong?


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The Tesla app lets you export daily usage data in CSV format. So I took this and lined up the monthly start/end dates to match my SCE bill. With Tesla's numbers, I subtracted the total "From Grid kWh" from the "To Grid kWh" and it shows I produced a net surplus of 108kWh for the month of June. But according to SCE, I actually consumed a net positive of 335kWh. So Tesla's data appears to be off by 443kWh, in other words a 132% error!

My Tesla reported usage has never aligned with my utility and I check it regularly online.There is something off on their (Tesla) side with home usage when a new day starts. Just take a look at that data at 12:01am. I’ve just learned to live with it.

 

[llamafilm]

I've looked closer at the breaker panel and now I see what's going on. The Powerblaster CT was installed around two wires: the incoming PV and the 100A line leading to my first subpanel. So all the additional circuits in this main panel are not being monitored by Tesla — this includes the car charger and also one of my two air conditioners. This seems like a mistake by Tesla's solar installer so I will have to give them a call on Monday. However, I'm not exactly sure how to correct it because the hot lines coming in from the grid meter are thick bus bars, not wires. It doesn't look like there would be enough space to fit the CT around those bars.

This is important because the Tesla app is the only way to track total monthly consumption. Te SCE bill shows net power purchased from them, but they do not track bought/sold separately.

 

[MCNE]

I've looked closer at the breaker panel and now I see what's going on. The Powerblaster CT was installed around two wires: the incoming PV and the 100A line leading to my first subpanel. So all the additional circuits in this main panel are not being monitored by Tesla — this includes the car charger and also one of my two air conditioners. This seems like a mistake by Tesla's solar installer so I will have to give them a call on Monday. However, I'm not exactly sure how to correct it because the hot lines coming in from the grid meter are thick bus bars, not wires. It doesn't look like there would be enough space to fit the CT around those bars.

This is important because the Tesla app is the only way to track total monthly consumption. Te SCE bill shows net power purchased from them, but they do not track bought/sold separately.

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Did they install a separate junction point with your install, something like this?

 

[llamafilm]

Did they install a separate junction point with your install, something like this?

I wasn't here for the install, the system came with the house when I bought it. But there is not a separate junction like that. The grid meter is located just above (and attached to) the main panel in my last photo. The 40A double pole breaker in the bottom right goes to the PV inverter. The 100A breaker feeds a subpanel which feeds most of the house. The remaining breakers in this main panel are for car charger, AC, and a couple of light fixtures. I'm not sure when the second AC was installed; it may have been after the solar. I'm guessing the solar installer decided to take a shortcut with the CT attachment, thinking those 2 little 20A breakers for lights were negligible.

 

[MCNE]

I wasn't here for the install, the system came with the house when I bought it. But there is not a separate junction like that. The grid meter is located just above (and attached to) the main panel in my last photo. The 40A double pole breaker in the bottom right goes to the PV inverter. The 100A breaker feeds a subpanel which feeds most of the house. The remaining breakers in this main panel are for car charger, AC, and a couple of light fixtures. I'm not sure when the second AC was installed; it may have been after the solar. I'm guessing the solar installer decided to take a shortcut with the CT attachment, thinking those 2 little 20A breakers for lights were negligible.

Crap, yeah you are correct they installed it wrong. Not sure what a solution would be with those bars not being accessible for the CT’s. Maybe an electrician would have a solution for you.

 

[llamafilm]

Tesla sent a technician out who is licensed in another state, so he was unfamiliar with the details of my system. He said it's weird that the existing CTs are clamped around 2 sets of wires: the 100A subpanel feed and the PV input wires. He seemed uncertain about this, but he decided to remove the PV wires from the clamp. Watching the Tesla app, this caused my consumption number to increase to a point that seems accurate now (excluding the extra breakers still not monitored).

His proposed solution is to add a CT splitter to the Powerblaster. This means there will be one set of clamps on the wires feeding the subpanel (which exits the top of the panel); and another set of clamps on a large bundle of wires including the 2nd air con, car charger, and 2 other 20A circuits (which all exit the bottom). I didn’t know a splitter was possible, but it’s much easier than replacing the whole panel and meter in order to clamp around the main input from the grid.