Viseu district
Solar panels in Castro Daire: what they produce
According to PVGIS, each kWp of panels facing south produces 1,475 kWh a year in Castro Daire, 3% below the median of Portugal's 308 municipalities (1,514 kWh). A 4 kWp system produces about 5,900 kWh a year here.
Castro Daire in numbers
kWh per kWp a year, facing south
At 35° tilt with 14% losses, from SARAH2 satellite data for 2005 to 2020 (PVGIS).
of Portugal's 308 municipalities
In Viseu district, it ranks 15th of 24.
kWh per kWp in July, the best month
In November, the worst, 1 kWp produces 80 kWh, 48% of the best month. An off grid system has to be sized for that month.
less on a roof facing east
West, 20% less; south east, 7% less; south west, 5% less.
A 4 kWp system in Castro Daire
- Yearly production
- 5,900 kWh
- Used at home (30%, the typical share)
- €430 a year
- Sold as surplus
- €210 a year
- Indicative price, turnkey, with VAT
- €5,500 to €7,500
- Payback
- 9 to 12 years
What you use saves about €0.24 per kWh; the surplus sells at about €0.05.
Run the numbers with your own billRules and the grid
Systems above 700 W and up to 30 kW need a prior notice on the DGEG portal, made by the installing technician before installation. In most of mainland Portugal the distribution grid belongs to E‑REDES, which assigns the production CPE.
On the map
Neighbouring municipalities
| Municipality | Distance between seats | kWh per kWp |
|---|---|---|
| Vila Nova de Paiva | 18 km | 1,501 |
| Tarouca | 20 km | 1,462 |
| São Pedro do Sul | 20 km | 1,481 |
| Resende | 21 km | 1,361 |
| Cinfães | 23 km | 1,390 |
| Lamego | 24 km | 1,482 |
Sources
- PVGIS, European Commission Joint Research Centre (yields per municipality, 1 kWp, 35° tilt, 14% losses, SARAH2 data for 2005 to 2020)
- Direção-Geral do Território, CAOP 2025 (official boundaries of the 308 municipalities)
- 4gnews, home solar prices in 2026 from DGEG certified installers in Lisbon, Porto and Coimbra, turnkey, 23% VAT included, 30 July 2026
- Eurostat, household electricity prices (nrg_pc_204), Portugal, 2,500 to 4,999 kWh a year, all taxes included, second half of 2025
- Fraunhofer ISE, Recent Facts about Photovoltaics in Germany, version of 26 August 2026 (self consumption without and with a battery)
- Portal Energia, the surplus regime in 2026 (fixed price around €0.05 per kWh)
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