insurance invalidation

For clarity, if you do a stupid job at your DIY solar installation and it burns your house down, that is likely a covered cause of loss. There isn't a policy exclusion for stupidity, unfortunately.

There may be an exclusion for the panels themselves since you could argue that improper workmanship was the proximate cause of loss, but the ensuing damage would likely be covered.

A similar scenario would be an improper plumbing repair flooding your house. Insurance won't pay to redo the plumbing that was wrong, but it will pay to fix the water damage.