First part of the system could be data collector of solar panels status.

There are two possible solutions how to collect the data:

1. Measure solar panels status directly.

2. Use invertor data available on RS 485 interface. They use Modbus protocol.

I prefer second option. It is a bit more complicated but DC power is a bit danger and I want sent data by WiFi local network to spare long wiring. Therefore I should have some intelligent device near the invertor anyway.

Compact solution is for me  unsuitable due to not enough room near the invertor and very long and complicated wiring to appliance. (heating)