What it yields where you are
How much solar produces in Napoli
In Napoli a well-oriented system produces 1,535 kWh a year for every kWp installed. A 6 kW system — a home-sized one — makes about 9,207 kWh a year. The figures below come from PVGIS, the European Commission's database.
1,535
kWh a year for every kWp
9,207
kWh a year from a 6 kW system
35°
the best tilt, facing south
01At a glance
A year of sun in Napoli.
A 6 kW system produces
9,207 kWh
About what 4.6 households use in a year.
The best month
July
1,019 kWh: 2.0 times the worst month.
Hours of sunshine a year
3,680 h
10.1 hours a day on average. In the leanest month it drops to 7.0.
How cloudy the sky is
45%
Average over the year. The cloudiest month is November, at 58%.
Warmest month's temperature
25.9 °C
In the coldest month the average is 8.7 °C.
How much it changes year to year
from −6% to +6%
Sunlight measured over the last twenty years, against the average.
02System sizes
How much a system produces in Napoli
The three sizes people actually put on a house, on the best plane.
3 kW
4,604
Produces each year · kWh
450 W modules: 7
6 kW
9,207
Produces each year · kWh
450 W modules: 13
10 kW
15,346
Produces each year · kWh
450 W modules: 22
03Month by month
Month by month in Napoli
A yearly total doesn't say when the energy arrives, and that's the part that decides whether you need storage.
A 6 kW system yields most in July, with 1,019 kWh, and least in November and December, with 519: 2.0 times as much. That's why the summer bill goes to zero and the winter one doesn't.
| Month | Output of 6 kW | Sunshine | Cloud | Temperature | Days above 30°C |
|---|---|---|---|---|---|
| January | 525 kWh | 218 h | 55% | 8.7 °C | — |
| February | 578 kWh | 233 h | 53% | 9.9 °C | — |
| March | 772 kWh | 295 h | 54% | 11.2 °C | — |
| April | 856 kWh | 328 h | 52% | 13.9 °C | — |
| May | 923 kWh | 368 h | 52% | 17.8 °C | — |
| June | 944 kWh | 396 h | 35% | 22.6 °C | 5 |
| July | 1,019 kWh | 429 h | 16% | 25.9 °C | 18 |
| August | 985 kWh | 392 h | 22% | 25.9 °C | 19 |
| September | 835 kWh | 322 h | 42% | 22.2 °C | 3 |
| October | 734 kWh | 272 h | 50% | 18.0 °C | — |
| November | 519 kWh | 214 h | 58% | 14.1 °C | — |
| December | 519 kWh | 213 h | 52% | 10.4 °C | — |
Heat costs yield: above 25 °C of cell temperature a panel loses about 0.4% per degree, and in summer the cell runs some twenty degrees above the air. Here there are 45 days above 30 °C a year, nearly all between June and September. That loss is already inside the figures above — don't subtract it twice — but it is why July, which gets the most sun of any month, never yields as much as the extra sun would suggest.
Output: our own calculation on PVGIS irradiation, calibrated against PVGIS city by city and month by month. Sunshine, cloud, temperature and hot days: ten-year averages 2015-2024 from the ERA5 reanalysis, via Open-Meteo. Two different sources, in separate columns on purpose.
04Orientation
And if the roof doesn't face south
Everyone asks this, and the answer in Napoli is: compared with a south-facing roof you lose about 19% facing east and 20% facing west, at the same tilt. Less than people expect — an awkward roof is still a good roof.
South-facing, 30°
1,529 kWh/kWp
The benchmark
East-facing, 30°
1,233 kWh/kWp
−19% compared with south
West-facing, 30°
1,231 kWh/kWp
−20% compared with south
05The years
And if next year is cloudy?
Fair question: the sun isn't the same every year. Here is how much it actually varied, from 2005 to 2024.
Over twenty years the poorest was 2010: 6% below average. The most generous was 2017: 6% above. Every other year sits in between. That's why a solar estimate uses the average of many years and not the last one — a bad year doesn't change the maths of a system that lasts twenty-five.
Yearly irradiation from 2005 to 2024 according to the ERA5 reanalysis, via Open-Meteo, against its own average. This is a different database from the one behind the output figures above, which comes from PVGIS and stops at 2023 — which is why the two periods don't match.
06For designers
The technical figures
The ones a designer needs. If you don't know them, you don't need them: everything is above.
Yield per installed kW
1,535 kWh/kWp
How many kWh each kW of panels gives in a year, on the best possible roof.
Best tilt
35°
The angle worth using here, facing south.
Sunlight reaching the ground
1,684 kWh/m²
Solar energy landing on one flat square metre in a year.
Other cities
Your roof isn't an average.
These figures are for an ideal roof in Napoli. The estimate on your address accounts for your roof, the shade and your consumption: two minutes, without leaving your contact details.