Tilt your solar panels to 40° facing south in G90. 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.
The G90 postcode district is centered 0.7 miles from Glasgow, at latitude 55.87°, and the angle above is measured at that center. A rule based on latitude alone would say 44°, 4° steeper than the measurement. Neighboring districts can differ by more than latitude would ever suggest: Ilkley and Otley in West Yorkshire sit almost exactly the same distance from the equator and measure six degrees apart, because Ilkley is down in Wharfedale.
Today, the most efficient tilt for photovoltaic panels in G90 is 59.3°, facing south. At solar noon the sun sits 30.7° 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. G90 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 40°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 31° facing south in summer months and 68.1° facing south in winter months.
When changing the angle of your photovoltaic panels each season, the most efficient angle is 27.1° facing south in summer months and 73.7° facing south in winter months, and 52.5° facing south in autumn and spring months.
If you adjust your photovoltaic panels every month, the table below gives the most efficient angle for G90 throughout the year. The shallowest angle is 32.5° in June, and the steepest is 79.3° in December.
| Month | Optimal tilt | Sun angle at noon |
|---|---|---|
| January | 76.0° | 14.0° |
| February | 67.1° | 22.9° |
| March | 56.3° | 33.7° |
| April | 44.3° | 45.7° |
| May | 35.8° | 54.2° |
| June | 32.5° | 57.5° |
| July | 35.5° | 54.5° |
| August | 44.1° | 45.9° |
| September | 56.1° | 33.9° |
| October | 67.7° | 22.3° |
| November | 76.3° | 13.7° |
| December | 79.3° | 10.7° |
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 G90 makes about 343 kWh a year, worth £89.51 at 26.11p per kWh, the Ofgem price cap for July to September 2026. Per kilowatt of panels that is 857 kWh, or £223.76, a year.
In G90, December is the worst month and generates 17% of what May does: about 21 kWh per kW of panels against 117. An array or battery sized for summer will come up short in December.
Averaged across the year, panels at the best fixed angle see 2.9 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.
For G90 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 40°.
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 44° 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:
Postcode district data contains 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.