Site location of a Solar PV Systems
As mentioned already, geographical and seasonal factors will inevitably impact upon the efficiency and output of your Solar PV installation.
Southern and coastal areas receive the most sunlight, although most areas of the United Kingdom are suitable for the generation of solar energy.
Since all panels in PV arrays are connected (unless you have micro-inverters installed), one panel receiving less light than the others will affect whole system's performance. For best system output, it is therefore necessary that your roof has little or no shade coverage. Even slight shade coverage can greatly reduce system output.
You can check the the level of sunlight that your area receives using the Met Office's solar irradiation map: http://www.metoffice.gov.uk/renewables/solar
Unsuitable property for Solar Panels