I bought a house about two years ago. A grid-tie solar electric system came with the house. It was already paid off -- no monthly subscription/payment required. The previous owner left a shoe box filled with cheap plastic electronic stuff labeled "Solar City". It turns out that Solar City sold out to Tesla a few years ago. After flipping through the documents and the stuff...it went into the trash.

There is a 2.4GHz antenna sticking out the bottom of the Aurora inverter. I presume this was supposed to provide data to the homeowner (and the installer) to monitor the system, but it required a secret password (and probably some money) to activate. So Claude and I dug into what it would take to extract the necessary data to monitor the performance of the system. 

We started out assuming nothing. Initial thinking was to use a current transformer around the output of the inverter to try and gauge the inverter power output over time. This led down a deep rabbit hole. I eventually asked Claude if the inverter could provide the data, since there was an antenna connected to it. After locating the owner's manual for the inverter Claude declared that it would be a simple matter to use the provided RS-485 interface to obtain the required data from the inverter. He found an open-source API that had the required information to interface with the inverter. Voila!

All we needed was a cheap SBC (a spare ESP32 board would do) and a RS-485 breakout board. We chose the Sparkfun RS-485 breakout board. It is a very simple circuit.

The ESP32 board is powered from a 5VDC wall wart. The ESP32 provides 3V3 to the RS-485 breakout board. No other components are required!

More later...