As I understand this credit, it is a non-refundable tax credit. If you do not have enough tax liability, then you'll not initiate a refund of the remainder. In this case, you must have a 9k tax liability for this year, or you'll just get the credit only for the tax you paid or owe up to this amount. If you had less than 9k, then you'll lose some of the credit, because you can't get a refund of this left over monies. But to be sure, call a tax pro!!! Or look on Web. for more information. Oh yeah, can't use this credit for new construction either as I understand.
I think that Mrs Reb and Jerry already explained the tax credit limits in clear detail. But there is one point in this post that needs clarification. I've highlighted it in red. The limited $1,500 max credit for windows etc only applies to existing homes. The "no upper limit" credit for geo, solar, etc.. applies to both existing and new construction.