How much will solar generate on a Milton Keynes roof?

The European Commission’s PVGIS model, run for the city centre at latitude 52.0406, longitude -0.7594 with the PVGIS-SARAH3 radiation database, a 35-degree pitch and 14% system losses, gives about 1,016 kWh a year per kWp facing south, about 809 kWh facing east and about 794 kWh facing west — so an east or west slope is roughly four-fifths of a south one and is still worth surveying. On that basis ten AIKO 485W panels, 4.85 kWp, facing south would be modelled at roughly 4,900 kWh a year before any shading. The seasonal swing is the number that matters for battery sizing: about 124 kWh per kWp in July against about 35 kWh in December. PVGIS does not model trees or neighbouring buildings, so we assess shading on site.