Tilt your solar panels to 39° facing south in Prince Rock. 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.
Prince Rock is in the PL4 postcode district, and the angle above is measured at that district's center, 0.7 miles from Plymouth. A rule based on latitude alone would say 41.3°, 2.3° steeper than the measurement, because latitude cannot see local cloud or the hills around a place.
Today, the most efficient tilt for photovoltaic panels in Prince Rock is 53.8°, facing south. At solar noon the sun sits 36.2° 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 south. Prince Rock is in the northern hemisphere, so panels catch the most sun facing south.
If you're mounting the photovoltaic panels at a stationary angle, such as on your roof, the most efficient angle is 39°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 25.8° facing south in summer months and 63.3° facing south in winter months.
When changing the angle of your photovoltaic panels each season, the most efficient angle is 22° facing south in summer months and 68.8° facing south in winter months, and 47.1° facing south in autumn and spring months.
If you adjust your photovoltaic panels every month, the table below gives the most efficient angle for Prince Rock throughout the year. The shallowest angle is 27.0° in June, and the steepest is 73.8° in December.
| Month | Optimal tilt | Sun angle at noon |
|---|---|---|
| January | 70.5° | 19.5° |
| February | 61.6° | 28.4° |
| March | 50.8° | 39.2° |
| April | 38.8° | 51.2° |
| May | 30.3° | 59.7° |
| June | 27.0° | 63.0° |
| July | 30.0° | 60.0° |
| August | 38.6° | 51.4° |
| September | 50.6° | 39.4° |
| October | 62.2° | 27.8° |
| November | 70.8° | 19.2° |
| December | 73.8° | 16.2° |
The sun angle at noon is how high the sun sits above the horizon at midday. Facing your panels south 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.
A 400W panel at its best fixed angle in Prince Rock makes about 440 kWh a year, worth £114.81 at 26.11p per kWh, the Ofgem price cap for July to September 2026. Per kilowatt of panels that is 1,099 kWh, or £287.03, a year.
In Prince Rock, December is the worst month and generates 29% of what May does: about 38 kWh per kW of panels against 133. An array or battery sized for summer will come up short in December.
Averaged across the year, panels at the best fixed angle see 3.7 peak sun hours a day. That is the figure to use when sizing an off-grid system, but size it for December rather than for the average, or it will run flat when you need it most.
PL4
For Prince Rock 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 39°.
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 41.3° 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:
Place names and postcode district coordinates contain OS data © Crown copyright and database right, and Royal Mail data © Royal Mail copyright and database right, used under the Open Government Licence v3. Fixed angle and generation measured with PVGIS at this location's own coordinates, © European Union, 2001-2026, CC BY 4.0. Electricity price from the Ofgem default tariff cap.