Peak Sun Hours in Phoenix, Arizona, United States
- Solar zone
- Zone 4 (excellent)
- Best month
- June (8.5)
- Worst month
- December (3.1)
- Climate
- Arid · 22.3°C
Monthly solar breakdown
| Month | GHI | Clear-sky | DNI | DHI | Temp °C | Humid % |
|---|---|---|---|---|---|---|
| Jan | 3.43 | 3.95 | 5.90 | 0.98 | 11.4 | 46 |
| Feb | 4.43 | 5.09 | 6.47 | 1.27 | 12.9 | 44 |
| Mar | 5.89 | 6.52 | 7.57 | 1.49 | 16.8 | 38 |
| Apr | 7.28 | 7.79 | 8.79 | 1.59 | 20.6 | 29 |
| May | 8.17 | 8.56 | 9.64 | 1.59 | 25.9 | 22 |
| Jun | 8.50 | 8.76 | 10.27 | 1.39 | 32.0 | 15 |
| Jul | 7.49 | 8.13 | 7.83 | 1.89 | 33.9 | 30 |
| Aug | 6.91 | 7.47 | 7.72 | 1.63 | 33.0 | 35 |
| Sep | 6.16 | 6.55 | 7.99 | 1.24 | 30.0 | 31 |
| Oct | 5.01 | 5.35 | 7.60 | 1.02 | 23.4 | 30 |
| Nov | 3.78 | 4.17 | 6.55 | 0.91 | 16.8 | 34 |
| Dec | 3.08 | 3.60 | 5.49 | 0.92 | 11.0 | 45 |
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 3.08 kWh/m²/day, 0.77 system efficiency.
About solar in Phoenix
Phoenix, United States has a dry climate with long hours of direct sunshine and low humidity. Its annual peak sun hours average 5.84 kWh/m²/day, a excellent solar resource by global standards.
The strongest month in Phoenix is June (summer) at 8.5 kWh/m²/day, and the weakest is December (winter) at 3.08 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.
Phoenix'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 Phoenix?
- Phoenix averages 5.84 peak sun hours per day annually, ranging from 3.08 in December to 8.5 in June.
- How many solar panels do I need in Phoenix?
- Panel count depends on your daily load. At Phoenix's annual average of 5.84 kWh/m²/day, a 5 kWh/day load needs roughly 3 × 400 W panels. Use the calculator above for your actual load.
- What size battery do I need in Phoenix?
- Sizing against Phoenix's worst month (December, 3.08 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 Phoenix's solar resource compare globally?
- Phoenix sits in solar zone 4 out of 5 (where 5 is strongest) at 5.84 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 often should I clean solar panels in Phoenix?
- Arid climates can drop output 10–20% between cleanings. Quarterly cleaning is typical for Phoenix; monthly during dust-storm seasons. Dew alone isn't enough when rainfall is infrequent.
- Does extreme heat hurt solar output in Phoenix?
- Yes. Panel efficiency drops ~0.4% per °C above 25 °C cell temperature. In Phoenix, midday cell temperatures of 55–70 °C can derate output 12–18% below nameplate.
- Is Phoenix's solar resource as strong as the numbers suggest?
- Phoenix's 5.84 kWh/m²/day is excellent globally. But heat derating and dust accumulation mean real-world yields typically land 10–15% below this headline figure — factor that into sizing.