Q: Is there a third party monitoring system that could be added to an existing system so that I can see more than just my net usage, but actually see if my solar panels are producing as I’d expect? Is there a way for people installing solar from the beginning to ensure that monitoring will remain available (open source access)? Is that common in single family homes?
A: Do you know who made your inverter? It is often SolarEdge or EnPhase. The app for your smartphone (and the web portal) comes from them not the installer. I think if you contacted them they could sort it out for you. If that does not work let me know. You will not be the only person in this situation as solar installers go bankrupt quite often.