How much does a 10 kW solar system cost in California?

What a 10 kW system costs, from California’s own data

California Distributed Generation Statistics publishes the average reported cost per watt of residential solar systems at PG&E, SCE and SDG&E, split into systems under 10 kW and systems of 10 kW or more. For 2025, systems of 10 kW or more averaged $4.26 per watt, which puts a 10 kW system at about $42,600 before incentives. The table shows each utility and the smaller-system average beside it.

Source: California DG Stats, cost per watt chart, residential, nominal dollars, data through May 31, 2026, checked September 23, 2026. The “10 kW at that average” column is our multiplication, not a published figure. For January to May 2026, the all-utility average for 10 kW and up was $4.35 per watt across 772 systems; PG&E had no 2026 figure in the chart.

How to read those averages

Four notes from DG Stats itself change how you should use the numbers:

• Self-reported. “All cost values are self-reported by applicants, and no additional verification has been performed.” The top and bottom 1% are removed.
• Solar only. The chart “samples single-technology applications that did not participate in a state subsidy program,” so systems sold with a battery are not in these averages.
• AC watts. Solar cost per watt is “represented using AC capacity.” Most quotes state the system in DC panel watts. Berkeley Lab calls the ratio of panel to inverter rating the inverter loading ratio; ask your quote for both numbers before comparing.
• Averages, not medians. A few expensive systems pull an average up, and the averages here are for whole utility territories.

The CPUC’s consumer guide points shoppers to the same database to see recent installation costs by ZIP code and adds that “these costs are not verified by the government” (CPUC). City-by-city permit fees and cost context are in solar panel cost by California city.

Why a 10 kW system can cost less per watt, and why yours might not

In the California data, systems of 10 kW or more averaged less per watt than smaller systems in every year from 2015 to 2026; in 2025 the gap was $4.26 against $5.11 (DG Stats).

Berkeley Lab is more cautious about recent national data: “Economies of scale are not especially evident among residential systems installed in 2025; other confounding factors may dominate the visual trends, though prior econometric analyses have shown clear effects.” It also found that soft costs and other balance-of-system costs were “roughly 80% of the total installed price” of residential systems in 2025 (Berkeley Lab, August 2026). So a larger system is not automatically a better deal per watt; the installer and the job matter more.

How much installers’ prices differ

A lot. Berkeley Lab ranked the top 100 U.S. residential installers by the median price of their host-owned systems in 2025: medians “ranged from $2.4 to $6.3/W,” “roughly 60% had median prices below $4/W, and almost 25% had median prices less than $3/W, while about 10% had median prices greater than $5/W.” Within one installer, project prices typically spanned $1 to $2 per watt. Berkeley Lab also says California, which dominates its sample, “is a relatively low-cost state for residential PV” (Berkeley Lab, August 2026).

On 10 kW, a $1 per watt difference is $10,000. That is why the CPUC tells shoppers to get bids from at least three qualified providers and warns that “the cheapest bid is not necessarily the best option” (CPUC). How to find and check installers is in comparing solar companies in California.

Is 10 kW the right size?

Probably larger than average. Berkeley Lab says the median U.S. residential system was 7.7 kW in 2025, “with most systems ranging from roughly 5-12 kW” (Berkeley Lab). Size should follow your electricity use:

• The CPUC says, “Typically, a system is sized to around 80-85 percent of your electricity use from the previous year,” and that it is “generally not in your financial interest” to install a system that produces more than you use in a year (CPUC).
• At PG&E, SCE and SDG&E, the CPUC says Net Billing customers are limited to no more than 150% of the past 12 months of use, and must attest that their use will rise to install an oversized system. Exported power is credited at values it says are “usually lower than the retail rate” (CPUC).
• SMUD allows up to 110% of your last 12 months of use, or 120% on its Solar and Storage Rate with a battery (SMUD).

How much a 10 kW array produces depends on your roof’s direction, tilt, shading and location. Run your address through NREL’s PVWatts calculator and compare its annual kWh with the production on your quote and with your last 12 months of use. A planned EV or heat pump is a reason to size up; a smaller bid is worth pricing too.

What the price does and does not include

• No federal credit. The IRS says the homeowner credit “is not available for any property placed in service after December 31, 2025” (IRS). A 2026 quote that subtracts 30% is using a credit you cannot claim.
• A battery is extra. Berkeley Lab found paired solar-plus-storage cash purchases had median prices $2.1 per watt higher than solar alone in 2025, and that about 80% of its paired-system price data came from California (Berkeley Lab). Put the battery on its own line; see home battery cost in California.
• Roof and electrical work. A roof replacement or main panel upgrade can be bundled into the price. Ask for each as a separate line so the solar price per watt compares.
• Loans cost more up front. Berkeley Lab found loan-financed systems “considerably higher priced than cash-purchase systems, potentially due in part to loan origination fees rolled into the up-front price.” Compare the cash price first; see solar dealer fees explained.

Check a 10 kW quote in three steps

1. Divide the cash price of the solar alone by its size in watts. Note whether the size is DC or AC.
2. Compare the result with your utility’s 2025 average above and with Berkeley Lab’s installer range. Well above both is a reason to ask why.
3. Put the quote, your bill and your usage into the solar quote calculator, and work out your payback period. If you would rather not buy, compare a lease, PPA or loan on the same system.

A referral request is optional and separate

California Rate Relief is a referral service. We are not a licensed contractor. The figures on this page are published averages and our arithmetic on them; a referral request does not produce a price, and only a written quote for your home does.