Ask which rate plan the projection assumes
Since April 15, 2023, customers applying for interconnection have taken service on the net billing tariff pursuant to CPUC decision D.22-12-056. Net billing tariff customers are paid for exported electricity based on its value to the grid, determined by the Avoided Cost Calculator, which varies by time of day.
The other half of the arithmetic is what you pay for the electricity you still buy, and that depends on your rate plan. Ask which specific plan your installer's savings projection assumes, and ask to see the same system modelled on at least one alternative.
Ask whether going solar moves you onto a different plan than the one you are on now, and what that change does to your bill before any solar production is counted. That baseline shift is easy to miss and it can be substantial.
A projection that names no rate plan is not a projection about your household. In a market where hourly pricing drives both halves of the calculation, that is a reasonable thing to insist on seeing.
When you use electricity is now part of the return
Electricity you consume as it is generated avoids a purchase at whatever your plan charges at that hour. Under hourly pricing, that makes the timing of household consumption a genuine financial variable rather than a curiosity.
The cheapest improvement available to you is behavioural. Running laundry, dishwashing and any vehicle charging during daylight raises the share of production consumed on site, and unlike equipment it costs nothing and can be changed at any time.
The harder part is the evening, when household demand typically peaks and production has faded. That is when electricity is most expensive and when a battery earns its return, by holding midday production until the hours that matter.
Ask your installer to model the self-consumed share explicitly and to 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.
Storage, and whether you qualify for help with it
A battery moves energy from a low-value hour to a high-value one, which under this tariff is a calculable return rather than a matter of preference. Ask for the arithmetic: kilowatt hours cycled per year, the value difference, the cost, and the payback period.
Ask separately what the system does during an outage. A grid-tied array without storage shuts down during an outage as a safety requirement, so if outage cover matters it has to be designed in, and a battery sized for bill savings is often not the same as one sized for meaningful backup.
California's Self-Generation Incentive Program provides incentives for battery storage that can function during a power outage, with $850 per kilowatt hour under its Equity category and $1,000 per kilowatt-hour under Equity Resiliency for qualifying customers.
Ask whether you might be eligible and confirm with the programme rather than treating a sales answer as final. Criteria and performance requirements are in the SGIP Handbook, and applicants have a year after reserving funds to meet them.
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.