I recently teamed up with a local installer to upgrade my old 5.2 kWh solar system from 2014 to a new 12 kWh setup, which includes a Tesla PW3 Battery and Inverter. The new array has panels on three different roof faces: 5.2 kWh facing South, and 3.44 kWh on both East and West faces. After starting net metering, I've noticed that the production is about 30% lower than what I anticipated. I modeled the output for the three different arrays using PVWatts, considering the pitch, the age of the 5.2 panels, and shading on the south face. The first six days of operation, we generated 195.9 kWh, while PVWatts predicted we should have produced 277.3 kWh, and the weather here has been mostly clear. I'm curious about potential reasons for this discrepancy.
2 Answers
You might want to look into the wiring of the strings. If they're not wired correctly or if there's a mismatch in the performance of the three separate strings, it could lead to lower overall output. I'm not sure if the Tesla app provides that info, but many systems can show production by string. If you haven't found it there, contacting support could clarify how to check each string's performance.
One possible reason for lower production could be insufficient PVCCs, which help optimize the output of your solar panels. If you're seeing a significant drop, it's worth checking how many are installed and if they're functioning properly. Sometimes, older panels can also underperform, especially if they have shading issues or are mismatched with newer technology. Might be good to get a diagnostic check on the system.