The federal residential energy credit is not refundable. That means, it can lower your tax liability to $0 so you get back all your tax withholding, but you don't get the rest. It's moved forward into the next year.
The IRS says, "The residential energy property credit is nonrefundable. A nonrefundable tax credit allows taxpayers to lower their tax liability to zero, but not below zero." See: Energy Incentives for Individuals: Residential Property Updated Questions and Answers
