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Tesla App Solar graph slightly higher than real value (Yes it's the CTs).

I always suspected that the Tesla app was over-estimating my solar output, as the home usage graph always had a slight bump up centered on solar noon. (Home usage = PoCo - Solar)
This weekend I opened up the panel and checked with my Fluke.
The actual situation is more complicated - the Current Transformer is only on one leg of the inverter output, so it's being 2x'ed in the gateway. I thought that was reasonable, but it does seem there is a balance offset, and for accuracy you would need to put both leg wires through the CT (one the opposite direction to the other). Then the 2x setting could be removed.

So what I'm seeing in the app right now is 2x of one leg that is slightly higher than the other. Not a huge deal, at the end of the month it's the electric company that uses their numbers. For automation purposes, I can use a rule that reads when I start to export at the gateway, which is a true 2 leg CT, to start EV charging.
 

holeydonut

Active Member
Supporting Member
Jun 27, 2020
3,366
2,766
East Bay NorCal
I always suspected that the Tesla app was over-estimating my solar output, as the home usage graph always had a slight bump up centered on solar noon. (Home usage = PoCo - Solar)
This weekend I opened up the panel and checked with my Fluke.
The actual situation is more complicated - the Current Transformer is only on one leg of the inverter output, so it's being 2x'ed in the gateway. I thought that was reasonable, but it does seem there is a balance offset, and for accuracy you would need to put both leg wires through the CT (one the opposite direction to the other). Then the 2x setting could be removed.

So what I'm seeing in the app right now is 2x of one leg that is slightly higher than the other. Not a huge deal, at the end of the month it's the electric company that uses their numbers. For automation purposes, I can use a rule that reads when I start to export at the gateway, which is a true 2 leg CT, to start EV charging.


I observe a similar issue, the Tesla readings are always about 8-10% higher than what is measured by my other monitoring tools (PG&E meter, Emporia Energy monitor, and my Enphase Envoy (the solar aggregator before generated energy hits the Tesla Gateway).

For example, at high noon, Tesla will measure my solar array generating 7.0 kW AC. This is impossible, my system peak is 1.21 amps x 23 microinverters x 240 volts = 6.7 kW AC, which is never achieved per readings on my Enphase Envoy (my peak is usually 6.5 kW AC).

Also, Tesla will read that my home uses like 30 kWh in a day, but my Emporia Vue will only 28 kWh. Even my PG&E meter disagrees with what Tesla says is exported/imported with the Grid.

I don't know why but Tesla is just always high. I've actually taken all my Tesla data and applied a 0.92x knockdown factor to get the resulting info to align better with my other data sources.

 

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