Establish who owns the array
The first question is whether the system is owned outright, financed with a loan, or subject to a lease or power purchase agreement. Those are three different situations and only the first is straightforward.
If there is a loan, find out whether it is being settled at closing or whether anything is expected to pass to you, and get that in writing as part of the transaction rather than as an assurance.
If there is a lease or a power purchase agreement, you do not get the array by buying the house. A third-party owner holds it, and you would generally have to qualify for and assume the agreement. Ask for the agreement itself, read the transfer terms, and find out what a buyout would cost.
Ask what the remaining term is and what the payment schedule looks like, including any escalation. A payment that rises annually for another fifteen years is a liability attached to the house and it belongs in your arithmetic about what to offer.
Find out which tariff the system is on
Since April 15, 2023, customers applying for interconnection have taken service on the net billing tariff pursuant to CPUC decision D.22-12-056. Systems interconnected before that date applied under earlier rules.
So a system on the roof of a house you are buying may be on a different arrangement from the one a new installation would get, and that difference is worth understanding rather than assuming. Ask the utility directly what arrangement the property is on, whether it transfers to a new owner, and what would happen to it if the system were expanded or replaced.
Ask that of the utility rather than of the seller or the agent, and get the answer in writing before closing. It is a specific question with a specific answer and it can materially affect what the system is worth to you.
Also ask what happens if you later add panels or a battery. Modifying an existing system can affect the arrangement it is on, and finding that out afterwards is an expensive way to learn it.
Condition, documentation and warranties
Ask for the permits, the inspection sign-offs, the interconnection approval and the equipment specifications with model numbers. A system without documentation is difficult to warranty, difficult to service and difficult to sell on again.
Establish who honours each warranty and how much term remains. Panels, inverter and workmanship are commonly covered by three different parties, and a company that has left the market cannot support a workmanship warranty however well it is written.
Ask about the roof underneath. If the covering is near the end of its life you will eventually pay to remove and reinstall the array, which is a real cost attached to the house that a listing will not mention.
Ask for production history if any exists. Actual generation over a year or two is far better evidence than a projection, and a system that has quietly underperformed is worth knowing about while you can still act on it.
What changed federally, and the battery incentive that remains
The 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025. A cash or loan purchase made now receives no federal credit, and a quote that still applies it is overstating your return substantially. Check any projection line by line rather than trusting a summary figure.
Section 48E survives at 30 percent and is available to third-party owners of residential systems under leases and power purchase agreements. The credit still exists, it simply no longer flows to a homeowner who buys the system. Expect lease providers to lead with that, and ask what they claim and what of that value actually reaches you in the rate offered, then confirm with a tax advisor.
California's Self-Generation Incentive Program continues to provide incentives for battery storage installed on the customer's side of the meter, including systems that can function during a power outage. Its Equity and Equity Resiliency categories are aimed at lower-income, medically vulnerable and at-risk for fire communities.
Depending on the category a customer qualifies for, the incentive is $850 per kilowatt hour under Equity or $1,000 per kilowatt-hour under Equity Resiliency. Applicants have one year after reserving funds to meet programme requirements, which include enrollment in a qualified Demand Response program, and further criteria are in the SGIP Handbook. Ask whether you might qualify and confirm with the programme rather than treating a sales answer as final.