Good luck with all of this.
The problem is I am assuming that most of the home owners may be clueless to Electricity, RF behavior, RFI and they may not even manage the solar collector systems in their homes.
Most will probably look at you like you have horns on your head. If they do shut something off and the noise stops, then all they are doing is setting themselves up for additional headaches in trying to resolve the problem.
Yes you may be able to get the FCC involved, but think about this. The problem could be a specific manufactured component, it would be with the installation or both.
If the system is generating "noise" it may be a problem, indicating an early failure or safety hazard, but again, will the homeowner even understand and know what steps to take to get a problem resolved.
Often you can use a Spectrum Analyzer along with receiver to track problems, trying to use your Radio Shack speaker system may not the best approach.
I have been stonewalled in the past with commercial business that had Neon sign lighting that was causing severe problems and the business is all the bit clueless and could care less, the sign company will take no action unless the business contacts them. So just be prepared for a long and difficult fight. You may luck out, you may have to live with things.
Good luck.