Peak Sun Hours in Terni, Umbria, Italy
- Solar zone
- Zone 3 (good)
- Best month
- July (7.2)
- Worst month
- December (1.5)
- Climate
- Temperate · 14.3°C
Monthly solar breakdown
| Month | GHI | Clear-sky | DNI | DHI | Temp °C | Humid % |
|---|---|---|---|---|---|---|
| Jan | 1.72 | 2.54 | 2.84 | 0.79 | 5.0 | 85 |
| Feb | 2.60 | 3.64 | 3.51 | 1.14 | 5.6 | 82 |
| Mar | 3.77 | 5.15 | 3.79 | 1.73 | 8.6 | 78 |
| Apr | 5.03 | 6.64 | 4.28 | 2.31 | 12.3 | 74 |
| May | 6.07 | 7.77 | 4.90 | 2.69 | 16.5 | 69 |
| Jun | 7.00 | 8.21 | 6.37 | 2.52 | 21.8 | 60 |
| Jul | 7.24 | 7.95 | 7.45 | 2.12 | 25.1 | 51 |
| Aug | 6.31 | 6.96 | 6.73 | 1.94 | 25.0 | 53 |
| Sep | 4.60 | 5.56 | 4.95 | 1.78 | 19.6 | 65 |
| Oct | 3.14 | 4.02 | 3.97 | 1.33 | 15.2 | 75 |
| Nov | 1.90 | 2.73 | 2.84 | 0.90 | 10.4 | 83 |
| Dec | 1.51 | 2.20 | 2.77 | 0.67 | 6.1 | 85 |
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 1.51 kWh/m²/day, 0.77 system efficiency.
About solar in Terni
Terni, Italy has a temperate climate with meaningful seasonal variation in solar resource. Its annual peak sun hours average 4.24 kWh/m²/day, a good solar resource by global standards.
The strongest month in Terni is July (summer) at 7.24 kWh/m²/day, and the weakest is December (winter) at 1.51 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.
Terni'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 Terni?
- Terni averages 4.24 peak sun hours per day annually, ranging from 1.51 in December to 7.24 in July.
- How many solar panels do I need in Terni?
- Panel count depends on your daily load. At Terni's annual average of 4.24 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 Terni?
- Sizing against Terni's worst month (December, 1.51 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 Terni's solar resource compare globally?
- Terni sits in solar zone 3 out of 5 (where 5 is strongest) at 4.24 kWh/m²/day — good 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 Terni?
- Terni's worst month (December) delivers 1.51 kWh/m²/day — about 21% of the summer peak of 7.24. Off-grid systems here typically oversize 1.5–2× or pair with a backup source.
- Do cloudy days significantly affect Terni's solar?
- Partly. Diffuse light still produces 10–25% of clear-sky output. Terni's 4.24 kWh/m²/day already reflects average cloudiness, so no further derating is needed for sizing.
- What panel tilt works best in Terni?
- At Terni's latitude (43°), a fixed tilt near 43° balances year-round yield. Winter-heavy loads favor latitude + 15°; summer-heavy, latitude − 15°.