Tilt your solar panels to 7° facing north in Lapão. 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 Lapão is 8.0°, facing north. At solar noon the sun sits 82.0° 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. Lapão 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 7°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 10.4° facing south in summer months and 29.2° facing north in winter months.
When changing the angle of your photovoltaic panels each season, the most efficient angle is 13.8° facing south in summer months and 34.1° facing north in winter months, and 8.9° facing north in autumn and spring months.
If you adjust your photovoltaic panels every month, the table below gives the most efficient angle for Lapão throughout the year. The shallowest angle is 0.2° in February, and the steepest is 34.8° in June.
| Month | Optimal tilt | Facing | Sun angle at noon |
|---|---|---|---|
| January | 8.7° | South | 81.3° |
| February | 0.2° | North | 89.8° |
| March | 11.0° | North | 79.0° |
| April | 23.0° | North | 67.0° |
| May | 31.5° | North | 58.5° |
| June | 34.8° | North | 55.2° |
| July | 31.8° | North | 58.2° |
| August | 23.2° | North | 66.8° |
| September | 11.2° | North | 78.8° |
| October | 0.4° | South | 89.6° |
| November | 9.0° | South | 81.0° |
| December | 12.0° | South | 78.0° |
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 Lapão, June is the worst month and generates 71% of what October does: about 114 kWh per kW of panels against 160. An array or battery sized for summer will come up short in June.
Averaged across the year, panels at the best fixed angle see 6 peak sun hours a day. That is the figure to use when sizing an off-grid system, but size it for June rather than for the average, or it will run flat when you need it most.
For Lapão 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 7°.
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 12.9° 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.