Tilt your solar panels to 18° facing north in Barão de Melgaço. That is the most efficient fixed angle for this exact spot, measured from satellite records of its sunshine and cloud rather than worked out from latitude. The full breakdown, including seasonal and monthly adjustments, is below.
Today, the most efficient tilt for photovoltaic panels in Barão de Melgaço is 12.9°, facing north. At solar noon the sun sits 77.1° above the horizon. Setting your panels to this angle keeps them as close to perpendicular to the sun as possible, which is where they generate the most electricity.
Your photovoltaic panels need to be angled facing north. Barão de Melgaço is in the southern hemisphere, so panels catch the most sun facing north.
If you're mounting the photovoltaic panels at a stationary angle, such as on your roof, the most efficient angle is 18°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 5.9° facing south in summer months and 33.4° facing north in winter months.
When changing the angle of your photovoltaic panels each season, the most efficient angle is 9.3° facing south in summer months and 38.5° facing north in winter months, and 13.7° facing north in autumn and spring months.
If you adjust your photovoltaic panels every month, the table below gives the most efficient angle for Barão de Melgaço throughout the year. The shallowest angle is 3.8° in January, and the steepest is 39.7° in June.
| Month | Optimal tilt | Facing | Sun angle at noon |
|---|---|---|---|
| January | 3.8° | South | 86.2° |
| February | 5.1° | North | 84.9° |
| March | 15.9° | North | 74.1° |
| April | 27.9° | North | 62.1° |
| May | 36.4° | North | 53.6° |
| June | 39.7° | North | 50.3° |
| July | 36.7° | North | 53.3° |
| August | 28.1° | North | 61.9° |
| September | 16.1° | North | 73.9° |
| October | 4.5° | North | 85.5° |
| November | 4.1° | South | 85.9° |
| December | 7.1° | South | 82.9° |
The sun angle at noon is how high the sun sits above the horizon at midday. Facing your panels north at the tilt shown for each month keeps them as close to perpendicular to the sun as possible, which is where they generate the most electricity.
In Barão de Melgaço, February is the worst month and generates 82% of what August does: about 110 kWh per kW of panels against 134. Size an array or battery for February, not for August, or it will come up short.
Averaged across the year, panels at the best fixed angle see 5.4 peak sun hours a day. That is the figure to use when sizing an off-grid system, but size it for February rather than for the average, or it will run flat when you need it most.
For Barão de Melgaço it is measured, not calculated. PVGIS, the European Commission's solar radiation model, works through years of satellite records of the sunshine and cloud at this exact coordinate and finds the fixed angle that collects the most light over a whole year. That is 18°.
Latitude sets the starting point, because it sets how high the sun climbs. It cannot see the rest: how cloudy the winters are, how much of the light arrives diffuse rather than direct, and whether hills block the low sun. A rule based on latitude alone gives 17.3° here. Even the best such rule, fitted to every city PVGIS has measured, misses a typical place by two and a half degrees, and a valley or a cloudy coast by far more. The seasonal, monthly and daily angles above do still come from latitude, because those follow the sun's height through the year, which latitude does determine. How the figures are worked out.
The angle is settled. Here is what is worth checking on the panels themselves:
Fixed angle and generation measured with PVGIS at this location's own coordinates, © European Union, 2001-2026, CC BY 4.0.