Honestly, I think it’s pretty fair. We have a minimum $30 monthly bill here in Upstate SC with Duke Energy. The basic “facilities fee” is usually around $15 or so for everyone, so in reality they’re charging you $15 more to support the grid since you are paying $0 in per kWh charges (that also pay for the grid). It’s similar to not buying gas and thus paying no gas tax bc you drive an EV. You still have to support the infrastructure like every other citizen.
Additionally, regardless of whether you use their power or not, the power company still has to service your address. You are NOT off the grid; you are still connected to their service. Therefore, you must support capital investments and the cost of them providing your address with service same as everyone else. Your solar benefit lies in not having to purchase and pay for power from them.
We can quibble about what that amounts to and what the minimum bill should be, but at the end of the day I think it’s fair on principle. Just my 2 cents.