If your total tax liability is 0 (zero) then the tax credit is carried forward to the next tax year.
Look at you federal tax return, Form 1040, on Line number 20 is the Home Energy Credits. If the tax liability is zero on lines 22 and 24. The amount of the credit will be carried forward.
Online editions -
Click on Tax Tools on the left side of the online program screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.