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Low Solar Production


Dec 1, 2020
Phoenix, AZ
Happy new year! Our system was PTO'd on Tuesday this week. 32x 340W panels (10.88 kW), SE10000H inverter, 3x Powerwalls. Here is a picture of the layout:


It's only been four days since we activated the system, but I'm concerned with the solar production so far. We live in a two story home in Phoenix, AZ. There are no trees or homes nearby to cast any shade on the panels.

Wednesday was our first full day of solar production. It was very sunny with not a cloud in sight. The solar production curve you see below is smooth, but total production was only 20.7 kWh for the day, with a peak of 3.5 kW.


Yesterday was a little overcast so the solar production curve is a little jaggy, and total production was only 14.3 kW with a similar peak of 3.5 kW.


Today was another day with zero clouds and production was only 20.2 kWh, with a peak of 3.4 kW.


I realize that the physical layout is a little funky due to the hip and valley roof, and that we're in the middle of winter when the sun is low. But these numbers still seem underwhelming for a system that borders on 11 kW capacity.

When I plug in our system configuration into the PVWatts Calculator, the yearly production estimate from NREL lines up with the one provided by Tesla in their system layout document (~17,500 kWh). However the PVWatts estimate for December is 27 kWh/day -- 33% higher than we're generating so far.

Additionally when I look at a handful of ~10 kW systems in my area on SolarEdge's public monitoring site, those systems show a similar production curve for today, but produced between 37 and 45 kWh, with peaks between 5.6 and 6.8 kW. That is considerably higher than what we've been producing so far, despite these being similar-sized systems in the same geographical area.

I'm going to call Tesla on Monday to ask for a SolarEdge account and see if I can get monitor the production of each panel a little more closely... Anything else you would recommend looking into?

I know this was a bit long, thanks for reading!


Active Member
Mar 28, 2017
Orlando, FL
On systems with powerwalls the solar production is monitored with a CT over feed from the inverters. It’s possible (and actually reasonably common) for there to be a misconfiguration where only half of your solar production data is actually reported by the app. I suspect that this is the issue you are running into and that you are actually producing about 20kWh per day with peaks of around 7kW. If this is the case tesla should be able to identify and correct the problem for you remotely when you call in to support.


Dec 13, 2020
We had an issue with calibration when we first started out after PTO. The most recent firmware seems to have fixed it but I haven't seen a full day of sun yet to tell. One thing I would mention is your system has very few southern facing panels- the two biggest arrays look to be north and east which are the two directions that produce the lowest. What is the pitch of your roof?


Apr 21, 2020
Fort Worth TX
only info you missed was your roof pitch... :(
run four arrays on pvwatts with the appropriate azimuth, make a spreadsheet and add them together... you might only get 26KW right now, i ran at 20 degree pitch.

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Apr 21, 2020
Fort Worth TX
zipped up spreadsheet

im wondering if they fu the strings. get them back to fix it. your inverter has 3 mpt controllers, i wonder how they wired your system. SE says east and west should be wired in series...
someone mentioned calibration of pw ct's... you might put a current meter on the output of the SE inverter and calculate/measure the output and compare to the tesla app...


  • phx_az_solar_example.zip
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May 29, 2020
Tucson, AZ
I think BrettS may have identified your problem.

Definately try to get the SolarEdge monitoring set up. Also try to get a by panel layout established on SolarEdge. I jsut noticed one of my panels is only producting about 60% of its neighbors.


Apr 21, 2020
Fort Worth TX
measure output of inverter with clamp amp meter... measure current of one leg of 240v, measure voltage of 240v, and multiply... or use multimeter that can do power..


Oct 27, 2019
I don’t get why Tesla does layouts like that. There are only 8 (south facing) panels that produce real energy in the winter months, so you are getting pretty much what you would expect. In the summer you will have more power than you can use though...


Well-Known Member
Mar 4, 2017
SF Bay Area
I think given the broken up roof design and having to adhere to ridgeline clearances (safety and fire) it’s hard to imagine better layouts really.

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