The best-selling photovoltaic panels are rectangular in shape and have a surface area of approximately 1.6 m².
The power delivered by each of these panels varies between 270 and 360 watts peak, depending on the type of panel (polycrystalline or monocrystalline) and the manufacturer, i.e. approximately 169 to 225 Wp/m².
Depending on the space available on your roof, you can add to the number of panels to multiply the total power of your installation. Larger panels also exist which are fitted to the roof in a single frame.
What is the optimal size in Brussels?
At the beginning of 2019, there were 3,335 photovoltaic installations in service in private homes in the Brussels-Capital Region.
The vast majority of these installations have a capacity of less than 5 kWp. Here's why:
- In Belgium, based on average sunshine levels, 1 kWp produces a maximum of 900 kWh per year under optimal conditions (south, 35°).
- In less favourable orientations, between 15° and 50° of inclination and for south-west to south-east orientations, this figure can drop by up to 8% (828 kWh).
- But it can fall even lower, by up to 50%, in really unfavourable conditions.
| To cover the needs of an average household (3,600 kWh/year), 4 kWp of power is therefore required under optimal conditions. This power can be provided by 17.5 to 23.5 m² of panels, depending on the type, or 11 to 15 panels. |
In the Walloon and Flemish regions, most domestic installations exceed 5 kWp, mainly due to more extensive housing and larger roof areas available.
What if the orientation is less favourable?
Simply compensate for the drop in efficiency by adding a few panels to achieve sufficient production. With the constant fall in the price of panels, this is no longer a problem.
And on my façade?
You have already perhaps seen this on some buildings: photovoltaic panels can nowadays also be fitted on façades.
However, the output is lower: the sun's rays do not fall vertically on their surface and there is therefore less sunshine. This lower output can be compensated for slightly by operating a larger surface area.
Important clarification: this type of panel, which can be seen from public areas, requires planning permission . Planning permission is not required, however, for panels built into an existing roof or which cannot be seen from public areas.