One could also argue that even if the solar panels are physically separate from the house, they are still considered to be "a physical part of" the property. Therefore the entire system is classified as residential rental real estate and depreciated over 27.5 years.
The panels themselves would be the only thing separate from the house, while all the other equipment to interface with the home's existing commercial electrical system would be "a permanent part of" the structure. It's not like if you sell the house, you can unplug the system and take it with you. Installation of this equipment generally requires a certified electrician and it must pass an inspection before the power company will allow it to be connected and/or activated on any structure that is a part of their electrical grid.
