Yes, Solar System for an RV and a boat have been accepted by the IRS as a second home for tax purposes. Click on Federal Tax Credit - Wholesale Solar
Qualifying equipment includes solar-powered units that generate electricity or heat water. The credit is only available for improvements you make to your residence. This can apply to a second residence as well. Costs for solar panels or related property that are installed as a roof or portion of a roof will not fail to qualify for the credit because they constitute a structural component of the roof (Instructions for Form 5695 - IRS.gov).
For additional information, click on Federal Tax Credit for Solar Energy - TurboTax Tax Tips & Videos
To enter your energy credit, click on How do I add or remove Form 5695?
