If the system was installed in 2023, you must claim it on your 2023 tax return. If there is an unused balance because the credit exceeds your tax liability , it will carry forward to 2024 and so on until used up. The fact that you might sell the home before the credit is used up does not affect your ability to use the carry forward credit. The fact that you financed the system also does not affect the credit carry forward (the need to assume the loan may affect the selling price of the home, but it does not affect the credit.)
This answer has been verified for accuracy by an Intuit expert employee
