They have clauses for this in the contract and also penalties for that.
Clearly the solution is to mine Bitcoin with the excess.
What percentage of rooftop solar homes is a net producer? I have a friend in that business at a different company. It would surprise me if even 1% of users produce more power than they consume.
When I put solar on my roof (In Illinois) they were trying to make me net zero overall, or a slight consumer of the grid: the utility net meters, but anything excess I send to the grid is worth zero dollars to me so there is no point in trying to generate extra.