Here is some more information--this is looking better and better.
"Does A Solar PV System For My Recreational Cabin Qualify?
The law states that the system must relate to a dwelling you use as a residence. It does specify or restrict the type of dwelling. Nor does it specify that it be a primary or permanent residence. Absent rulings to the contrary, primary residences, summer (or winter) homes, recreational cabins, summer camps, boats, motor homes, etc that are used as a residence by the taxpayer should all qualify as dwellings. The credit is attached to the taxpayer, though, so you are limited to a credit for one system."
Full page can be found here:
Solar Power Tax Credits for US Residents | Alternative & Renewable Energy - ABS Alaskan, Inc.