California solar resources: the official tools, data and rules worth bookmarking

Sunlight and production: the solar resource itself

Engineers use “solar resource” to mean how much sunlight a place gets. That is the starting point for every production estimate in a quote. You do not need the raw data, but it helps to know where an installer’s numbers come from and how to check them.

PVWatts calculatorNational Renewable Energy Laboratory

Estimates the energy production of grid-connected photovoltaic systems for a location, for homeowners, building owners and installers.

When to use it: Use it to sanity-check the yearly and monthly production in a proposal. NREL notes that version 8 estimates may differ from earlier versions depending on location and inputs.

National Solar Radiation Database (NSRDB)National Renewable Energy Laboratory

Hourly and half-hourly weather data with the three standard measures of sunlight: global horizontal, direct normal and diffuse horizontal irradiance.

When to use it: This is the “solar resource” in the technical sense: how much sun a place receives. Most homeowners reach it through PVWatts rather than directly.

A proposal should show production month by month, not just a yearly total, because the winter months produce less and the bill math depends on when power is made. The guide to winter solar production in California explains why a December bill looks different.

Checking a solar company before you sign

Each of these takes a few minutes and costs nothing. Use them on every company you are considering, including any this site refers you to.

Check a LicenseContractors State License Board

Searches contractor licenses by number, business name or personnel name, and salesperson registrations by number or name.

When to use it: Before a second meeting with any installer, and again on the day you sign. The database is offline Sunday 8 p.m. to Monday 6 a.m.

Public Data Portal: licensees by classification and countyContractors State License Board

A free spreadsheet of currently renewed licenses for up to 10 classifications and 10 counties, with status, bond and workers’ compensation details.

When to use it: When you want every licensed C-46 Solar or C-10 Electrical contractor in your county rather than the few names a map search shows.

Solar energy system disclosure requirementsContractors State License Board

The rules for the disclosure document that must sit on the front page of a residential solar contract, with the documents for 3-day and 5-day cancellation periods.

When to use it: While reading a contract, to confirm the total cost, complaint process and cancellation rights are all there.

California Solar Consumer Protection GuideCalifornia Public Utilities Commission

The state’s plain-language guide to buying, leasing and financing solar. Version 4 was published in 2025.

When to use it: Before you request quotes. It advises bids from at least three qualified providers and explains your right to cancel.

How to use them together is covered in the contractor verification walkthrough and the statewide guide to choosing a solar company.

Your bill and the export credit

The value of solar depends on how your utility bills you after it is installed. For customers of the three big investor-owned utilities, the CPUC sets those rules. Municipal utilities such as LADWP, SMUD and Roseville Electric publish their own.

Net energy metering and the Net Billing TariffCalifornia Public Utilities Commission

How PG&E, SCE and SDG&E customers are credited for exported solar, including the Net Billing Tariff that applies to interconnection applications since April 15, 2023.

When to use it: When a proposal models your future bill. The export credit it assumes should match the tariff you will be on.

California Distributed Generation StatisticsCPUC-overseen data site

Every solar system interconnected under net metering in PG&E, SCE and SDG&E territory, updated monthly with about a six-week delay.

When to use it: To see how much solar is being connected in your area. It does not cover municipal utilities such as LADWP or SMUD.

For what the rules mean in practice, see NEM 2.0 versus net billing and the California utility rate tracker.

Tax credits, rebates and financing rules

Incentives change more often than anything else on this page, so go to the agency’s own page before you count on one. As of September 23, 2026, the federal residential credit no longer applies to new installs, and the most useful state-level items are the property tax exclusion and the income-qualified programs.

Residential Clean Energy CreditInternal Revenue Service

The federal 30% credit for home solar and batteries of 3 kWh or more, available for property installed from 2022 through December 31, 2025.

When to use it: Only if your system was completed by the end of 2025. It is not available for property placed in service after that date.

Active solar energy system exclusionBoard of Equalization

The rule that keeps a qualifying solar installation from raising your property assessment. It is an exclusion, not an exemption.

When to use it: If you are worried about property taxes. The statute is scheduled to sunset on January 1, 2027.

Low-income solar programsCalifornia Public Utilities Commission

DAC-SASH no-cost rooftop systems for income-qualified homeowners in disadvantaged communities, SGIP storage incentives and bill-discount programs.

When to use it: Before paying market price, if your household income may qualify.

IRA residential energy rebate programsCalifornia Energy Commission

The HEEHRA and HOMES rebates for heat pumps and electrification. Solar panels are not on the list.

When to use it: If you are pairing solar with a heat pump. Single-family HEEHRA rebates were fully reserved statewide as of February 24, 2026.

PACE financingDepartment of Financial Protection and Innovation

How PACE loans work: payments are added to your annual property tax bill, and DFPI has licensed PACE program administrators since 2019.

When to use it: Before agreeing to any financing that goes on your property tax bill; DFPI warns PACE contracts are difficult to void.

The overview of California solar incentives ties these together, and the Inflation Reduction Act page explains what happened to the federal credit.

Market data and building rules

These are for context: what systems have cost, how much of the state’s power is solar, and what the building code now requires on new homes.

Tracking the SunLawrence Berkeley National Laboratory

Installed-price and design trends for distributed solar across the United States, with a public data file.

When to use it: For a price benchmark. Its 2024 edition put most host-owned residential systems installed in 2023 between $3.20 and $5.50 per watt.

California electricity dataCalifornia Energy Commission

Statewide generation by source. Solar was 21.30% of total system power in 2024, before counting rooftop systems.

When to use it: For context on where California’s power comes from and how much rooftop solar displaces.

2025 Energy Code: single-family solar PVCalifornia Energy Commission

The solar requirement for newly built single-family homes, including how system size is calculated and the exceptions.

When to use it: If you are building or buying a new home permitted on or after January 1, 2026.

A plain-language reading of the generation data is in what share of California’s power is solar.

Which resource to use at each step

1. Deciding whether to look at solar at all: your last twelve months of bills, the CPUC’s net billing page and the consumer protection guide.
2. Choosing who to ask for quotes: the CSLB contractor list for your county, then the license check on each name.
3. Comparing quotes: PVWatts for the production estimate, the Tracking the Sun price range for context, and the same line items from every bidder.
4. Paying for it: the IRS, BOE and CPUC pages for what incentives still apply, and DFPI’s PACE page before any property-tax financing.
5. Signing: the CSLB disclosure requirements, read against the front page of the contract you are handed, and a second license check on the day.

Tools on this site

This site is a referral service, so treat its tools as a second opinion next to the official resources above. The bill and quote calculator works out a quote’s price per watt and checks its bill estimate against your own bill. The California solar cost index and the city cost guides cover what goes into a price, including the San Diego solar cost guide for SDG&E customers. The statewide solar panel guide pulls the cost, rules and incentives into one place.