"100% Self powered" but still receiving charges for energy import

[fehguy]

Hi everyone, I have solar tiles and 2 power walls in sunny (and sometimes smokey) California. As of mid April I have been--according to the Tesla app--100% self powered, however I am receiving non-trivial energy import readings from my electric company:

April: 42kWh
May: 46kWh
June: 82kWh
July: 64kWh

At the same time I'm exporting ~200kWh per month, in addition to powering my house and charging my cars. I am aware that I could be draining the battery below reserve and requiring grid input but I have been quite careful about timing of energy use and have not seen a single incident of this.

Is the app lying? Is the utility company lying? There are no other taps into our electricity that could go around the power walls so I'm baffled. I have opened a case with my electric company to see what's going on, but would love to hear from others if "100% self powered" is an aspiration or factual reporting from the app.

 

[arnolddeleon]

Feels about right for what I'm seeing. I think "self-powered" vs "balanced" in the app setting does slightly better. I'm guessing you are running "balanced" " cost saving". It's nigh impossible to be perfect because the system has to respond to the load and try balance it. The animation even kinda indicates this that it sometimes pulls from/pushes to the grid even when it is in "self-powered" mode. I've looked at the meter during the day when I'm supposed to be at zero load and I can see it flipping which direction the power was flowing. I also have Sense installed and can see the some slight mismatches.

Tesla did discover a minor issue with the Powerwall CTs that improved the matching on my system once it was fixed.

Here is snippet of my PG&E detailed bill. July would have had lower charges except there was a "StormWatch" event and there was one day that I ran out of battery while I experimenting with the settings.

 

[getakey]

Hi everyone, I have solar tiles and 2 power walls in sunny (and sometimes smokey) California. As of mid April I have been--according to the Tesla app--100% self powered, however I am receiving non-trivial energy import readings from my electric company:

April: 42kWh
May: 46kWh
June: 82kWh
July: 64kWh

At the same time I'm exporting ~200kWh per month, in addition to powering my house and charging my cars. I am aware that I could be draining the battery below reserve and requiring grid input but I have been quite careful about timing of energy use and have not seen a single incident of this.

Is the app lying? Is the utility company lying? There are no other taps into our electricity that could go around the power walls so I'm baffled. I have opened a case with my electric company to see what's going on, but would love to hear from others if "100% self powered" is an aspiration or factual reporting from the app.

what do the graphs in the app look like?

 

[fehguy]

I think because my power company doesn't integrate costs correctly with Tesla, I don't have the "Balanced" option in my app. Images below of app settings and the graphs.

 

[getakey]

do the daily power flow graphs show any power coming from the grid?

 

[zƬesla]

I'm on self-powered. Lowest electric bill "purchase" was 5kW a couple of months ago.

 

[fehguy]

@getakey I see tiny blips, presumably when the PW is syncing with the grid. My power company just got back to me, said "looks like everything is working normally".

 

[MorrisonHiker]

I think because my power company doesn't integrate costs correctly with Tesla, I don't have the "Balanced" option in my app. Images below of app settings and the graphs.

The Balanced option is under Advanced - Time-based control.

 

[getakey]

I think you need the power company to prove it

 

[sorka]

I think because my power company doesn't integrate costs correctly with Tesla, I don't have the "Balanced" option in my app. Images below of app settings and the graphs.

What does the app actually say exported and imported from the grid?

 

[Will792]

The only option that I see is to check meter daily for import number.

I actually question accuracy of Tesla readings. I compare mine with solar RGM and Enphase solar/consumption meters and the difference is substantial, 3%-4%.

 

[mike95]

Hi everyone, I have solar tiles and 2 power walls in sunny (and sometimes smokey) California. As of mid April I have been--according to the Tesla app--100% self powered, however I am receiving non-trivial energy import readings from my electric company:

April: 42kWh
May: 46kWh
June: 82kWh
July: 64kWh

At the same time I'm exporting ~200kWh per month, in addition to powering my house and charging my cars. I am aware that I could be draining the battery below reserve and requiring grid input but I have been quite careful about timing of energy use and have not seen a single incident of this.

Is the app lying? Is the utility company lying? There are no other taps into our electricity that could go around the power walls so I'm baffled. I have opened a case with my electric company to see what's going on, but would love to hear from others if "100% self powered" is an aspiration or factual reporting from the app.

Very simple. I had similar confusion once I went with Tesla solar and battery. The definition of self powered means some form of assistance, either solar or battery. So even if say solar contributes 1kw continuously throughout the day while the rest comes from grid, the app will consider this self powered, which is true, just not fully self powered. Same applies with battery.

 

[charlesj]

The only option that I see is to check meter daily for import number.

I actually question accuracy of Tesla readings. I compare mine with solar RGM and Enphase solar/consumption meters and the difference is substantial, 3%-4%.

I don't have the Enphase consumption part just solar generation. Comparing that quantity to the Tesla app for solar generation is 0.5% apart at most at end of day. If I check and compare during the daytime it is off due to integration differences but later at night it if super accurate. Revenue sensors are in two classes from what I was told, 0.2% and 0.5%.

 

[Will792]

I don't have the Enphase consumption part just solar generation. Comparing that quantity to the Tesla app for solar generation is 0.5% apart at most at end of day. If I check and compare during the daytime it is off due to integration differences but later at night it if super accurate. Revenue sensors are in two classes from what I was told, 0.2% and 0.5%.

Here is comparison of my Tesla and Enphase readings for yesterday:
55.6KWh PV production reported by Tesla and 53.6 by Enphase. 43.9 house consumption in Tesla and 35.7 in Enphase. I have whole house backup option installation so Enphase and Tesla readings should match for consumption.

BTW my grid voltage is somewhat on the hot side. It is rather common that I have 247V-249V coming from the grid. Unfortunately my utility company has 5% acceptable policy for over voltage so anything below 253 is considered to be acceptable. It is possible that Enphase assumes 240V in calculations but I somewhat doubt it.

 

[fehguy]

I think I got to the bottom of this. Yesterday I shut off the main breaker to see if anything would stop working and surprisingly, my AC heat pump shut off. It seems like somehow it was wired up to bypass the Powerwall and go straight to the grid. Surprisingly, the AC air handler is fully backed up, so there must be something odd about how they wired things up into my main panel. This is going to be a tough one to explain to the installers who put the AC unit in.

I have a single main panel with 250 amps which feeds the power wall and 2 sub panels, along with the AC heat pump and air handler. So it feeds 4 circuits in total. I really don't know enough about how these are set up to understand how it works. I would have expected that the power wall would sit between all the circuits on the main panel but clearly that's not right.

 

[sorka]

I think I got to the bottom of this. Yesterday I shut off the main breaker to see if anything would stop working and surprisingly, my AC heat pump shut off. It seems like somehow it was wired up to bypass the Powerwall and go straight to the grid. Surprisingly, the AC air handler is fully backed up, so there must be something odd about how they wired things up into my main panel. This is going to be a tough one to explain to the installers who put the AC unit in.

I have a single main panel with 250 amps which feeds the power wall and 2 sub panels, along with the AC heat pump and air handler. So it feeds 4 circuits in total. I really don't know enough about how these are set up to understand how it works. I would have expected that the power wall would sit between all the circuits on the main panel but clearly that's not right.

So basically your heater is backed up but the AC isn't? Doesn't sound too hard to explain.

 

[fehguy]

@sorka it's not hard to understand conceptually . It's hard for me to understand how this was done in the same electrical panel.

 

[Bitslizer]

@sorka it's not hard to understand conceptually . It's hard for me to understand how this was done in the same electrical panel.

Need more detail... any pictures of the 250a panel? Do you have a TEG2? How is that wired? or a backup switch? where are the site CT clamps located? Can you share your 3 line diagram from Tesla?

 

[fehguy]

Need more detail... any pictures of the 250a panel? Do you have a TEG2? How is that wired? or a backup switch? where are the site CT clamps located? Can you share your 3 line diagram from Tesla?

I will get a photo of it tonight and pull up the diagram from Tesla (although, they diverged from it during the install)

 

[ArizonaJon]

I have 2 PWs and the AC compressor is backed up so the battery and/or PV system can operate in case of a grid failure. BUT I had to have a soft start device installed to reduce the AC starting current (LRA current) as it exceeds what the 2 PWs can provide. I understand that some AC compressor cannot use a soft start. You may not be able to back up you AC compressor. Most can use soft start, so you will need to have this installed before you add the AC compressor to the backed up devices.

The other thing I have done is remove the car EVSE from the system if the grid fails. If the car was charging and the AC compressor came on it would trip the batteries.