# Solar Panel Efficiency Calculation

edited November -1
Is there a calculation for the amount of power my system should be creating? I have a 12.2k system, but am tracking it every 5 minutes using the API to the gateway...over the past 4 months since the PTO, I have averaged 9.681kw during peak times. I realize there is a loss coefficient, but wanted to find what is normal loss and if my system seems to be functioning at full intended capacity.

Thanks!

• edited August 2019
It can vary depending on when your system was installed and who made the panels. There is no single equation that can be used across all panel. That said, you should have info in your TESLA contract that states how much energy you should make by month and over the life of the system.
For reference: I have a 4.8kW array made up of 16 of the 300 watt panels feeding an inverter rated at 4.2kW. System was installed July 2018 and over this year it rarely hit the inverter max unless there was some cloud edge magnification going on. So, you should check your contract, then do a little GOOGLE on the issue. You may be a tad disappointed, but efficiency is what it is - but it IS getting better as advances are mainstreamed.
• edited August 2019
An industry rule of thumb is that the DC max rating of the panels (rarely achieved except in a lab) to the AC max rating of the inverter is about 1 : .80. In other words, the inverter is typically rated at about 80% of the array rating. Lots of variables, location being just one. My ratio is 84%, but I've got great roof pitch, my array faces directly South, and I'm in the Sun belt (So. CA). I still get clipping a few times a year, but it's really rare. Clipping looks like a flat spot on top of your daily solar production curve.

9.68k to12.2k is pretty close to 80%, so I'd not worry about it.
• edited August 2019
Agree with Gregbrew.

FWIW we rarely see more than 10-11 kW of average generation from our 14 kW total panel capacity. The system was designed that way, giving us just enough annual generation to zero-out our electric bills. On average we generate/consume about 2 MWh of energy per month.
• edited August 2019
BTW, The calculations were all done by the Tesla installation analysis algorithms, and are baked into the production guarantees *in your contract*. That's what you should be comparing to...YOUR production against YOUR contract. With the dozen+ different variables involved in every system installation, comparing them to each other in anything but the most gross sense is not a worthwhile endeavor.