Thank you for the response. With respect to my roof, it was nearly 100 years old. There were 3 layers of shingles over the original wood shake, and the solar panels could not be installed without a complete tear down. The solar contractors assured me that the whole project cost was eligible for the tax credit under those circumstances. If that's not correct, that changes things somewhat.
Secondly, I went back to my 1040, and all I see on lines 24-31 are the taxes that had been withheld. Without the solar credit, as noted previously, the calculation was that I owed $9767. The only thing I changed was taking out and putting back in the amount for the solar credit. So I don't think the withheld taxes are the explanation.
