Your tax situation is completely separate from any contract you have with the solar company. Your credit is not affected by the fact that you are selling the house before paying for the system in full. You will continue to receive the carry forward credit on your tax return according to the normal calculations and rules for the credit. For example, suppose the cost of the system was $30,000. You should have claimed the full price of the system when it was installed, even though you were getting a loan. The credit would have been $10,000. (Shown on line 13 of form 5695). If, because of your other tax situation, you only got $8000 of the credit in 2023, you would carry forward $2000 which will probably be paid to you in 2024. (see line 16 of your form 5695).
What obligations you have to the solar panel installer is between you and them, and doesn't change your tax return.
Of course, you will be completely unable to sell the home unless one of 2 things happens:
a. you pay off the solar loan in full so the new owners can have a clean title, or
b. the new owners agree to assume the loan and the solar company agrees to allow the loan to be assumed.
