There's only two options   Type of Asset - F  rental furnishings    or  I - Rental Real Estate       well maybe three because you could choose   O - other 

So if the neighbor came over and said "hey I really like your solar system can I buy it?"    could it be removed and sold without tearing into the property?   If no - then it is part of the real estate.   Doesn't a solar system require lots of "plumbing" installation.