Peak sun hours in California
California averages 5.8 peak sun hours a day across the year, 4th of the 50 states. At that figure a 400-watt panel produces about 1.79 kWh a day after real-world losses, and covering the 900 kWh average US bill takes about 17 panels. Los Angeles, the state's biggest city, sits a little under the statewide figure at 5.6 hours, so 5.8 is the midpoint of a spread that leans away from the largest population centre.
strong sun: 5.8 of a possible ~6.5 hours
Panel counts for California bills
Computed at California's 5.8 hours with 400W panels and the 0.77 derate; the US-average column shows what the same bill takes at 4.5 hours, so you can see what your state's sun is worth in hardware.
| Monthly usage | California | System size | US average |
|---|---|---|---|
| 500 kWh/mo | 10 panels | 4 kW | 12 panels |
| 750 kWh/mo | 14 panels | 5.6 kW | 18 panels |
| 900 kWh/mo | 17 panels | 6.8 kW | 22 panels |
| 1,000 kWh/mo | 19 panels | 7.6 kW | 24 panels |
| 1,500 kWh/mo | 28 panels | 11.2 kW | 36 panels |
| 2,000 kWh/mo | 37 panels | 14.8 kW | 48 panels |
What 5.8 hours means in practice
California sits in the strong tier of American sun, 4th of 50 at 5.8 hours, 29% above the national average. In panel terms the 900 kWh average bill needs 17 panels here instead of the US-average 22. Systems this far into the Sun Belt usually pencil on production alone; the variables that actually kill quotes here are shade and roof direction, not the resource.
How a California year is shaped
The 5.8-hour figure is an annual average, and no month is average. These are the twelve monthly means for California from NASA's 2001-2020 solar climatology, each as a share of the state's own annual mean, with that share applied to the 5.8-hour planning figure. June and December are marked.
| Month | Share of the annual average | Peak sun hours (est.) |
|---|---|---|
| January | 49% | 2.9 |
| February | 67% | 3.9 |
| March | 92% | 5.3 |
| April | 118% | 6.8 |
| May | 139% | 8.1 |
| June | 154% | 8.9 |
| July | 149% | 8.7 |
| August | 136% | 7.9 |
| September | 112% | 6.5 |
| October | 83% | 4.8 |
| November | 57% | 3.3 |
| December | 43% | 2.5 |
California's curve tops out in June at 154% of the annual average and bottoms in December at 43%, a 3.5-to-one spread with 48% of the year's light landing in four months. In hours: 8.9 a day at the peak, about 2.5 in December.
Half the California calendar sits above the annual average and half below: April through September are the six months that beat it, carrying 67% of the year's light. April is already worth about 6.8 hours a day, so the productive half of the year starts earlier than most people expect.
Bills here are small, which changes the shape of the whole decision: EIA put the average California household at 503 kWh a month in 2024, 42% under the national 863 and among the lowest in the country. 10 panels cover it across a year, and 22 would be needed to cover it from December sun alone, 2.2 times as many. That is a narrow enough gap that storage sized for a California December is an ordinary purchase rather than a project-killer, which is not true in most of the country.
California is one of the states where a statewide number does the most damage: it has the 5th widest internal spread of the fifty. Across the 20 grid cells sampled here the southeast runs 26% sunnier than the northwest. Held against the 5.8-hour statewide figure that is roughly 6.6 hours at one end and 5.0 at the other, which is the difference between two quite different quotes. Nobody should size a California roof off the state average without checking which end of the state it sits on.
What that sun is worth on a California bill
| EIA, 2024 residential averages | California | United States |
|---|---|---|
| Average home's monthly use | 503 kWh | 863 kWh |
| Price per kilowatt-hour | 31.97¢ | 16.48¢ |
| Average monthly bill | $160.86 | $142.26 |
| One 400W panel, a year's output | 652 kWh | 506 kWh |
| What that output displaces | $208 | $83 |
Power is expensive here, and that is most of the story. At 31.97¢ a kilowatt-hour California was the 2nd dearest state in 2024, 94% above the national 16.48¢, so every kWh a panel makes is worth 94% more than the same kWh in an average state. One 400-watt panel offsets about $208 of California electricity a year against $83 at national sun and national prices. Expensive power is the strongest argument for solar there is.
California lands in much the same place on both rankings, 4th for sun and 2nd for what a panel earns, so its position in the sun table is a fair guide to its position on value. That is not automatic. Utah gets less sun (5.5 hours to California's 5.8) and pays 12.22¢ against 31.97¢, so one panel is worth about $133 more a year in California than in Utah.
Two warnings on those dollar figures. They are displaced electricity and nothing else: no install cost, no incentive, no financing, and no assumption about how your utility settles a surplus, which is the single biggest unknown in the sum. And a state average hides the utility you are actually on; 31.97¢ is every California residential customer averaged together, and neighbouring territories can differ by more than the gap between two states in the ranking.
Getting a number for your address
For a location-exact figure, run your address through NREL's free PVWatts; it uses measured weather for your grid cell and will also model roof tilt and direction, which statewide numbers cannot. Then compare its annual kWh against a quote's promise before you sign anything.
Questions people ask
How many solar panels do I need in California?
About 17 400-watt panels (6.8 kW) for the 900 kWh a month an average US home uses, at California's 5.8 peak sun hours. For the average California home specifically, which EIA measured at 503 kWh a month in 2024, it is 10. Your own bill is the variable that matters, and the calculator takes any figure.
Is 5.8 peak sun hours good for solar?
Yes, comfortably. California ranks 4th of the 50 states, 29% above the national average, which means fewer panels per kWh of bill than almost anywhere else in the country.
How much is one solar panel worth a year in California?
About $208. One 400-watt panel at California's 5.8 peak sun hours makes roughly 652 kWh a year after the 0.77 derate, and California residential electricity averaged 31.97¢ a kilowatt-hour in 2024 (EIA), which puts California 2nd of the 50 states on this measure against 4th on sunlight alone. That figure is displaced electricity only. It says nothing about install cost, incentives, or how your utility settles a surplus.
Do peak sun hours change with the seasons in California?
Yes, by a factor of 3.5 here. NASA's 2001-2020 climatology puts California's June at 154% of the annual average and December at 43%, so the 5.8-hour figure on this page is the midpoint of a curve running from roughly 8.9 hours a day down to 2.5. Grid-tied homes bank the summer surplus as credit; off-grid designs have to size for the trough, and in California that means 22 panels for an average local bill instead of 10.