Solar · California
How many solar panels do I need in California?
For the average California home, which uses 503 kWh a month (EIA, 2024), about 9 × 400 W solar panels (3.37 kW) facing south at the best tilt. One kW of panels in California makes about 1,792 kWh a year, 5.6 kWh a day in August and 3.8 in December, the 4th sunniest of 51.
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Solar output by month in California
Output falls to 68% of the August level in December. Grid-tied homes are sized on the year; anything off-grid has to be sized for December.
| Month | kWh per kW | Per day | 200 W panel, Wh/day into a battery |
|---|---|---|---|
| January | 125 | 4.03 | 685 |
| February | 128 | 4.57 | 776 |
| March | 158 | 5.09 | 866 |
| April | 162 | 5.40 | 918 |
| May | 162 | 5.22 | 888 |
| June | 157 | 5.24 | 891 |
| July | 170 | 5.50 | 934 |
| August | 174 | 5.60 | 952 |
| September | 159 | 5.29 | 899 |
| October | 149 | 4.81 | 818 |
| November | 131 | 4.37 | 742 |
| December | 118 | 3.79 | 645 |
Charging a power station in California
A 200 W panel propped up facing south refills a 1,000 Wh power station in about 1.1 days in August and 1.6 days in December. To refill it in one day you’d need about 220 W of panels in August and 320 W in December. Check your station and panel →
A balcony or plug-in panel in California
A 400 W panel hanging upright on a south-facing railing makes about 443 kWh a year, worth about $132 at California’s average rate (29.75¢/kWh, August 2026), if you use the power as it’s made. Shade and the rules where you live matter more than anything here. Try your kit →
The rules in California: California law (SB 868, Chapter 985, 2026; signed September 30, 2026, takes effect January 1, 2027) on plug-in solar says: “Has a maximum aggregated AC output of no more than 1,200 watts per dwelling.” … “may require a customer using a portable solar generation device to notify the electrical corporation or local publicly owned electric utility, using a simple online registration form, of the address, make, model, and size of the portable solar generation device”. Check with your utility before connecting. Official source: California Legislative Information, SB 868, text as archived October 2, 2026; checked November 5, 2026. Every state we track →
Across California
California’s figure is the population-weighted average of Los Angeles, San Diego and San Jose, its three largest cities; across them, a kW makes 1,789 to 1,793 kWh a year.
| City | Population (2024) | kWh per kW a year |
|---|---|---|
| Los Angeles | 3,878,704 | 1,793 |
| San Diego | 1,404,452 | 1,791 |
| San Jose | 997,368 | 1,789 |
Cross-check: an estimate from NASA POWER sunshine came out at 1,754 kWh per kW, 2% below the Global Solar Atlas figure. Within our 12% threshold.
Electricity rates and appliance costs in California →
FAQ
How many solar panels do I need in California?
For the average California home, which uses 503 kWh a month (EIA, 2024), about 9 × 400 W solar panels (3.37 kW) facing south at the best tilt. One kW of panels in California makes about 1,792 kWh a year, 5.6 kWh a day in August and 3.8 in December, the 4th sunniest of 51.
How much does a solar panel produce in California?
A 400 W panel facing south at the best tilt makes about 717 kWh a year in California: about 69 kWh in August and 47 kWh in December (Global Solar Atlas).
How long does a 200 W solar panel take to charge a 1,000 Wh power station in California?
About 1.1 days in August and 1.6 days in December, propped up facing south, at 85% charging efficiency. Lying flat, about 2.6 days in December.
How many solar panels for the U.S. average home in California?
The U.S. average home uses 863 kWh a month (EIA, 2024). In California that takes about 5.78 kW: 15 × 400 W panels.
Is there still a federal solar tax credit?
Not under the residential credit for systems installed after 2025: the IRS says the section 25D credit will not be allowed for any expenditures made after December 31, 2025, and an expenditure counts as made when installation is completed.
Sources and assumptions
- Solar output (kWh per kW of panels, by month): Global Solar Atlas 2.0, long-term averages to 2025 (data version 2.2.68, updated 2026-04-01), for crystalline-silicon panels facing south at the best fixed tilt, after typical system losses. Data obtained from the “Global Solar Atlas 2.0, a free, web-based application is developed and operated by the company Solargis s.r.o. on behalf of the World Bank Group, utilizing Solargis data, with funding provided by the Energy Sector Management Assistance Program (ESMAP). For additional information: https://globalsolaratlas.info” Licensed CC BY 4.0; we rounded and combined it as described here. Not affiliated with or endorsed by Solargis or the World Bank Group.
- State figure: population-weighted average of the state’s three largest cities (U.S. Census Bureau Vintage 2024 population estimates; coordinates from the 2020 Census Gazetteer). Hawaii and DC use one city.
- Cross-check: NASA POWER sunshine climatology (2001–2025), tilted with a standard isotropic-sky model × 0.80. States more than 12% apart were reviewed by hand; the gaps are explained on our methodology page.
- Home use: EIA Table 5A, 2024 average monthly residential kWh by state. Rates: EIA Electric Power Monthly, August 2026.
- Tax credit: IRS FAQ on the One, Big, Beautiful Bill (FS-2025-05, Aug. 21, 2025).
- Assumptions: 85% charging efficiency into a battery, 85% from battery to appliance, panel counts rounded up, off-grid sizing for the worst month.