Peak Sun Hours in San Jose, California, United States
- Solar zone
- Zone 4 (excellent)
- Best month
- June (8.3)
- Worst month
- December (2.2)
- Climate
- Temperate · 14.0°C
Monthly solar breakdown
| Month | GHI | Clear-sky | DNI | DHI | Temp °C | Humid % |
|---|---|---|---|---|---|---|
| Jan | 2.42 | 3.27 | 3.93 | 0.96 | 8.3 | 84 |
| Feb | 3.46 | 4.43 | 4.91 | 1.23 | 9.2 | 83 |
| Mar | 4.79 | 5.92 | 5.68 | 1.66 | 10.7 | 82 |
| Apr | 6.22 | 7.35 | 7.03 | 1.80 | 11.9 | 78 |
| May | 7.47 | 8.30 | 8.59 | 1.75 | 14.5 | 73 |
| Jun | 8.33 | 8.73 | 10.36 | 1.36 | 17.6 | 66 |
| Jul | 8.20 | 8.42 | 10.32 | 1.23 | 19.6 | 62 |
| Aug | 7.36 | 7.59 | 9.53 | 1.19 | 19.8 | 63 |
| Sep | 6.01 | 6.30 | 8.48 | 1.06 | 19.4 | 60 |
| Oct | 4.40 | 4.82 | 6.94 | 0.99 | 16.3 | 63 |
| Nov | 2.93 | 3.53 | 5.07 | 0.92 | 11.7 | 73 |
| Dec | 2.17 | 2.92 | 3.84 | 0.84 | 8.4 | 81 |
GHI, Clear-sky, DNI, DHI in kWh/m²/day. Data: NASA POWER climatology (long-term monthly averages).
Off-grid calculator
Add appliances
- Add an appliance to size a system.
Sizing
- Daily load
- 0.00 kWh
- Panel wattage
- 0 W
- Panel count (400W modules)
- 0
- Battery bank
- 0.0 kWh
Sizing against worst-month PSH of 2.17 kWh/m²/day, 0.77 system efficiency.
About solar in San Jose
San Jose, United States has a temperate climate with meaningful seasonal variation in solar resource. Its annual peak sun hours average 5.31 kWh/m²/day, a excellent solar resource by global standards.
The strongest month in San Jose is June (summer) at 8.33 kWh/m²/day, and the weakest is December (winter) at 2.17 kWh/m²/day. When sizing a year-round off-grid system, it's standard practice to design against the December value rather than the annual average — otherwise the battery bank runs low during the darkest weeks.
San Jose's solar conditions are well within the range where off-grid PV is a straightforward engineering exercise with standard-sized arrays and lithium batteries.
FAQ
- What are the peak sun hours in San Jose?
- San Jose averages 5.31 peak sun hours per day annually, ranging from 2.17 in December to 8.33 in June.
- How many solar panels do I need in San Jose?
- Panel count depends on your daily load. At San Jose's annual average of 5.31 kWh/m²/day, a 5 kWh/day load needs roughly 4 × 400 W panels. Use the calculator above for your actual load.
- What size battery do I need in San Jose?
- Sizing against San Jose's worst month (December, 2.17 kWh/m²/day) with 2 days of autonomy at 80% depth of discharge, a 5 kWh/day load needs about a 12.5 kWh battery bank.
- How does San Jose's solar resource compare globally?
- San Jose sits in solar zone 4 out of 5 (where 5 is strongest) at 5.31 kWh/m²/day — excellent by global standards. For reference, top-tier desert sites average ~6.5 and high-latitude cities around 2.5 kWh/m²/day.
- How much does winter reduce solar output in San Jose?
- San Jose's worst month (December) delivers 2.17 kWh/m²/day — about 26% of the summer peak of 8.33. Off-grid systems here typically oversize 1.5–2× or pair with a backup source.
- Do cloudy days significantly affect San Jose's solar?
- Partly. Diffuse light still produces 10–25% of clear-sky output. San Jose's 5.31 kWh/m²/day already reflects average cloudiness, so no further derating is needed for sizing.
- What panel tilt works best in San Jose?
- At San Jose's latitude (37°), a fixed tilt near 37° balances year-round yield. Winter-heavy loads favor latitude + 15°; summer-heavy, latitude − 15°.