Rooftops are excellent sites, but panels can also be mounted at ground level. Unlike wind or hydro (water) power, solar PV panels can easily be sited in urban areas. Roof mounted panels are usually a ‘permitted development’, so you won’t need planning permission. Exceptions include National Parks, conservation areas and listed buildings.
Ideally, PV panels should be roughly south-facing and free of shade at an angle of 20 to 50 degrees. As the figure below illustrates, the perfect roof for a PV roof in the UK is facing due south and has a tilt angle (pitch of the roof) of around 35°. The figure shows that a PV roof that is facing due east or west and has a steeper tilt angle of 40° will produce 20% less electricity than one mounted in a perfect position (tilt angle is the angle of your roof taken from the horizontal, as shown here).
Another factor that influences the performance of a PV roof is the geographical location. As the solar radiation map of the UK (below) illustrates, a site in Cornwall will receive 30% more solar energy than one in northern Scotland.
Our Solar Calculator can be used to estimate the electricity produced by a PV roof in a given location with a given orientation and tilt of the roof.