Does have a lease or loan attached to it?
We would strongly recommend the loan or lease be paid for upon the sale. The honest reason these are pain in the ass.
Step 1. Ask the buyer for the installation documents and loan/lease documents.
Step 2. ask the buyer to pay the system off with the home sale.
Step 3. Is it working? How do you know? Have it certified and the panels washed for the new buyer.
Step 4. Have the inspection report sent to the buyer.
Step 5. Transfer ownership of the solar system to the Buyer. This might include a few steps, even some paperwork and even an installer.
Step 6. Fix anything wrong with the solar system.