What it yields where you are
How much solar produces in Trieste
In Trieste a well-oriented system produces 1,325 kWh a year for every kWp installed. A 6 kW system — a home-sized one — makes about 7,950 kWh a year. The figures below come from PVGIS, the European Commission's database.
1,325
kWh a year for every kWp
7,950
kWh a year from a 6 kW system
39°
the best tilt, facing south
01At a glance
A year of sun in Trieste.
A 6 kW system produces
7,950 kWh
About what 4.0 households use in a year.
The best month
July
910 kWh: 2.4 times the worst month.
Hours of sunshine a year
3,336 h
9.1 hours a day on average. In the leanest month it drops to 5.2.
How cloudy the sky is
54%
Average over the year. The cloudiest month is November, at 65%.
Warmest month's temperature
24.8 °C
In the coldest month the average is 5.1 °C.
How much it changes year to year
from −8% to +7%
Sunlight measured over the last twenty years, against the average.
02System sizes
How much a system produces in Trieste
The three sizes people actually put on a house, on the best plane.
3 kW
3,975
Produces each year · kWh
450 W modules: 7
6 kW
7,950
Produces each year · kWh
450 W modules: 13
10 kW
13,250
Produces each year · kWh
450 W modules: 22
03Month by month
Month by month in Trieste
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 910 kWh, and least in December, with 374: 2.4 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 | 426 kWh | 180 h | 60% | 5.1 °C | — |
| February | 514 kWh | 187 h | 62% | 6.8 °C | — |
| March | 720 kWh | 276 h | 54% | 9.3 °C | — |
| April | 771 kWh | 310 h | 53% | 13.0 °C | — |
| May | 808 kWh | 334 h | 62% | 17.2 °C | — |
| June | 846 kWh | 385 h | 47% | 22.3 °C | 4 |
| July | 910 kWh | 409 h | 40% | 24.8 °C | 12 |
| August | 864 kWh | 380 h | 40% | 24.7 °C | 14 |
| September | 737 kWh | 300 h | 47% | 19.9 °C | 1 |
| October | 592 kWh | 242 h | 57% | 15.5 °C | — |
| November | 390 kWh | 175 h | 65% | 10.5 °C | — |
| December | 374 kWh | 158 h | 61% | 6.6 °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 30 days above 30 °C a year, nearly all between June and August. 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 Trieste is: compared with a south-facing roof you lose about 21% facing east and 21% facing west, at the same tilt. Less than people expect — an awkward roof is still a good roof.
South-facing, 30°
1,313 kWh/kWp
The benchmark
East-facing, 30°
1,034 kWh/kWp
−21% compared with south
West-facing, 30°
1,035 kWh/kWp
−21% 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 2014: 8% below average. The most generous was 2022: 7% 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
1,325 kWh/kWp
How many kWh each kW of panels gives in a year, on the best possible roof.
Best tilt
39°
The angle worth using here, facing south.
Sunlight reaching the ground
1,411 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 Trieste. The estimate on your address accounts for your roof, the shade and your consumption: two minutes, without leaving your contact details.