Sun hours are not the same as output
Ask what temperature assumptions sit behind your production estimate, and whether the model was run for your specific location and roof rather than derived from a regional average. That question separates an installer doing engineering from one filling in a template.
Ask to see monthly figures rather than an annual total. The annual number hides the shape, and the shape is what tells you whether the system will meet your expectations in August rather than on average.
Ask how the array is mounted and how that affects operating temperature. Airflow beneath the modules matters in a climate like this, particularly on a low-slope or tightly flush installation where heat has less opportunity to escape.
Ask for a shading assessment covering the whole year rather than the hour of the site visit. Shading costs more than people expect because it removes production in the middle of the day, when the array is otherwise at its strongest.
What the production is actually worth
Since April 15, 2023, customers applying for interconnection have taken service on the net billing tariff pursuant to CPUC decision D.22-12-056. Exported electricity is paid at its value to the electric grid, determined by the Avoided Cost Calculator, rather than at the retail rate.
So a large annual production figure is not the same as a large return. What matters is how much of that production you consume yourself, avoiding a retail purchase, and what the rest is worth at the hours it is exported.
The utilities are required to publish uniform machine-readable spreadsheets containing the retail export compensation rates on their websites. Ask which values your installer used and check them against the published figures rather than accepting a summary.
Ask for the self-consumed share to be modelled explicitly. A heavy afternoon cooling load helps considerably here, because it means production is consumed rather than exported, which is the more valuable outcome under this tariff.
The roof it all sits on
Panels outlast most roof coverings, and intense sun with extreme summer heat ages roofing faster than a year count suggests. Ask for a condition assessment rather than an age estimate.
If the covering is within a few years of replacement, replace it first. Removing and reinstalling an array to reach the roof underneath is a cost with no offsetting benefit whatsoever, and it is entirely avoidable while you are still quoting.
Ask how mounting penetrations are flashed and sealed, what method the roofing manufacturer approves for your covering type, and what the workmanship warranty covers on them and for how long. Leaks around mounting hardware are the most common physical failure in residential solar.
Establish who honours each warranty. Panels, inverter and workmanship are commonly covered by three different parties on three different terms, and a company that has left the market cannot support a workmanship warranty however well it is written.
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.