Insist the estimate is about your roof
Ask whether the production estimate was modelled for your specific roof, orientation and shading, or derived from a regional average. In a city with this much variation between neighbourhoods, a regional average is close to meaningless.
Ask for a shading assessment covering the whole year rather than the hour of the site visit. Neighbouring buildings, trees and the city's own topography create shading patterns that shift substantially between seasons.
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 a foggy stretch or a short winter.
Orientation is the decision that most affects output and it cannot be recovered later with better equipment. A south-facing unshaded plane produces the most, east and west planes produce usefully but give up output, and a north plane rarely repays the hardware.
Older buildings, complicated roofs
Panels outlast most roof coverings, so a covering within a few years of the end of its life should be replaced before the array goes on. Removing and reinstalling a system to reach the roof underneath is a cost with no offsetting benefit at all.
Ask for a condition assessment rather than an age estimate, and consider getting it from a roofer rather than only from the company selling you solar. Ask how many layers of covering are present and what the structure underneath is, and whether anything needs reinforcement to carry the array.
Ask how mounting penetrations are flashed and sealed, and what method the roofing manufacturer approves for your covering type. Leaks around mounting hardware are the most common physical failure in residential solar and they usually appear a few years in.
On a small or complicated roof, ask how the usable area was calculated and what setbacks or access requirements reduce it. That determines the largest system you can actually fit, which is often well below what a roof looks like it should hold.
What the tariff means for a smaller system
Since April 15, 2023, customers applying for interconnection have taken service on the net billing tariff pursuant to CPUC decision D.22-12-056, and are paid for exported electricity based on its value to the grid, determined by the Avoided Cost Calculator.
Electricity you consume as it is generated avoids a purchase at the retail rate, which is generally worth more than exporting it at midday. On a constrained roof that is actually reassuring: a smaller system matched to daytime household consumption is closer to the right answer under this tariff than it would have been under retail-rate crediting.
Ask your installer to model the self-consumed share explicitly and value the remainder at the published export rates. The utilities are required to publish uniform machine-readable spreadsheets containing those rates on their websites, so the figures are checkable.
Then ask what the same system looks like with storage, which moves midday production into the higher-value evening. Ask for the arithmetic rather than the recommendation, and ask whether you might qualify for SGIP.
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.