What Can I Do About Solar Panel Shading From Tall Trees?

As the number of residential solar panel installations increase there is going to be a greater problem from over shadowing or shading from trees and other obstacles. Trees in particular will cause a problem as even partial shading on some solar arrays can significantly reduce their ability to generate electricity.

In the UK there are many types of tree that can grow taller than a standard residential property. If there happens to be a tall tree opposite to your south facing roof there could be a potentially significant impact on your solar photovoltaic panels or even solar thermal panels. This is even more so the case with semi-evergreen and evergreen trees such as the dreaded Leylandii which can grow up to a metre a year and reach heights of 35 metres tall.

How shading affects Solar PV Panels

Most of the solar panels that are used in residential installations in the UK are prone to power loss through shade. They tend to be overly sensitive to even partial shade, this means that you can end up with a significant loss in power output even if only part of the array is shaded.

If one of your neighbours has a high evergreen hedge or tree that gets in-between your solar panels and the Sun this means they will be in shadow. Unless it is a particularly tall tree that is very close to your south facing roof the shadow problem will only usually be significant during winter. In winter the Sun moves across the horizon at a much lower angle and so is more likely to be obscured by obstacles.

During the winter evergreen trees stay green and so block out all the light. Deciduous tree lose all their leaves in winter and so light can pass through greatly reducing the shadowing effect. Tall evergreen trees such as Leylandii along your south facing border may already cause roof shading or may do so in the future due to their fast rate of growth.

Installing PV panels on a shadow prone roof

If you are considering getting a solar photovoltaic panel system installed the surveyor should point out any potentially problems with shadowing. They will be able to explain to you the potential loss in generated electricity due to any existing shading or potential shading in the future.

As far as the law goes you only really have any come back if the trees that are causing a problem are evergreen, specifically Leylandii. If you believe that one of your neighbours evergreen trees is or will cause a problem you can take action. It is best to negotiate with your neighbour in the first instance. Also check with your installer who will probably had plenty of experience with this type of issue.