How much solar energy can your roof capture?

You can install solar panels on almost any property and any type of roof, including the sloped and flat roofs of your house, summerhouse, pool house, shed and even your detached garage. Of course, the roof must be in good condition, sufficiently stable and have the necessary load-bearing capacity. It’s also worth knowing that not every roofing material is suitable for installing solar panels. While it doesn’t matter what type of property it is (i.e. whether it’s terraced, detached or a farmhouse), you should always check whether you need a permit. 

The exact yield of a solar panel system varies from roof to roof. How much sunlight your roof can capture depends on a number of key factors that we’ve laid out below.

Let’s start with a quick lesson you may have had in primary school: the sun rises in the east and sets in the west. It reaches its highest point in the south at noon. It may sound obvious, but ideally you should place solar panels facing east, south and west to generate the most electricity possible. Of course, this isn’t possible for every roof. 

• South-facing solar panels generate a lot of energy, peaking at noon (panels facing south-east or south-west are a good alternative).
• East or west-facing panels produce a good amount of energy in the morning or before sunset.
• Panels facing both east and west ensure that energy generation is spread throughout the day.

Whatever you do, you should definitely avoid installing solar panels that face north, north-west or north-east as they won’t generate enough to be worthwhile on even the sunniest summer days.

• Panels installed on a sloped roof have to follow the angle of the roof.
  The angle of the roof and the orientation are also connected: for sloped roofs facing south, south-east or south-west, an acute (but not too steep) angle is ideal, while sloped roofs facing east or west should have a smaller, flatter angle.
• A flat roof allows you to choose the angle of your solar panels
  They are often installed at only a slight angle because otherwise you need a more expensive mounting structure or the panels may protrude beyond the edge of the roof. A slight angle also allows more panels to fit on your roof because the shadows they cast will have less of an impact.
  

To get the most from your solar panels, you obviously need to make sure that they avoid shadows wherever possible. If you’re not sure which parts of your roof are shaded, wait for a spring or summer day and take a look where your roof is in shadow and for how long. Dormers, chimneys, trees, posts, other parts of the roof and neighbouring properties can all cast a shadow. You should also bear in mind that trees and shrubs will grow as the years go by.

Shadows falling across your roof before 9 a.m. or after 5 p.m. aren’t too bad, and even a little bit of shade at other times of day isn’t a real issue. That being said, shadows will reduce the efficiency of the panels they fall across, and they can even affect the entire installation if your panels are connected in series. Thankfully, there are technical solutions that allow you to somewhat mitigate the impact of shadows.

Just because you have a big roof doesn’t mean that the whole roof is suitable for installing solar panels. For example, some areas may not be able to bear the weight, the distance between the ridge and the edge of the roof may not be large enough, or space may be taken up by chimneys and skylights. Each solar panel requires around two square metres, and you need to install at least four solar panels to make your installation cost-effective.

If you’re wondering whether your roof is suitable for solar panels and which parts of it receive the most sunlight, contact an installer. They’ll take a closer look at your situation and tell you where solar panels should ideally be installed. The additional ‘Solar panels and battery’ service in KBC Mobile enables you to find a reliable and skilled installer thanks to our partner ‘Impact us today’. What’s more, you can use KBC Mobile to get an initial personal estimate of what it would cost to install solar panels. Try it for yourself!