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Solar panels on flat roof

If you are thinking of installing solar panels , you must take into account if the roof has a slope or is a flat roof, this article is dedicated to how to install solar panels on a flat roof.

Solar panels on flat roof

Installing solar panels on a flat roof is an even more interesting investment than with a sloped roof. With a flat roof, there is more freedom to make an installation plan. This generally leads to higher returns and a shorter payback period.

Do you have a flat roof and want to install solar panels? Read in this article what specific things you should pay attention to. So you already have a lot of knowledge when you talk to the installer.

How many solar panels fit on the roof?

By changing the tilt angle, orientation, and location (horizontal or vertical) of the solar panels, you can change the number of solar panels that fit on the roof. The first question to ask yourself is “how many solar panels do I need?” We answer this in our article on solar panel measurements.

In general, you buy enough solar panels to neutralize your electricity consumption. The average electricity consumption is as follows:

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type of home Electrical consumtion
1 person 1,800 kWh
2 people 2,950 kWh
Family (1 child) 4,000 kWh
Family (2 children) 4,600 kWh
Family (3 children) 5,300 kWh


orientation of the solar panels.

On a flat roof you have the option to choose which direction you want to install the solar panels. It is ideal for placing solar panels facing south.

Sometimes people choose to place solar panels in an east-west position. The amount of electricity generated is therefore less per solar panel, but more solar panels can fit on the roof. As a result, the installation as a whole produces more energy.

The orientation of the solar panels has the following effect on performance but it depends on the geographical location of your house:

Orientation performance
South 100%
Southwest /  Southeast 95%
East West 80%
North fifty%
Northwest /  Northeast 60%

Solar panels in horizontal or vertical position

With mounting frames, the solar panels can be placed in a horizontal or vertical position. In a vertical position, more solar panels fit side by side, but the space between two rows increases. By varying this, along with the orientation and tilt angle, the installation of a solar panel can be optimized.

Solar panels on flat roof

Slope and space between panels.

When installing solar panels on a flat roof, it is important to consider the angle of inclination and the distance between the panels. It’s a shame if the solar panels cast a shadow on the panels behind them.

This is the effect of the angle of inclination on the installation:

slope  angle performance Distance to next panel *
35° 100% 1.30 meters
30° 99% 1.28 meters
25° 98% 1.25 meters
20° 97% 1.22 meters
15th 95% 1.18 meters
10th 93% 1.13 meters
87% 1 meter

* this refers to a panel with a height of 1 meter. The distance is the distance from point A to point B in the figure below. The results are finalized, the specific result depends on your location in the Netherlands.


Solar panels on flat roof

The formula used is as follows: distance AB = panel height * sine (180 – α – β) / sine β

In the formula, α is the angle of inclination of the panel, β is the latitude of the location.

A solar panel installer can fully advise you on this.

How big should the no-go zone be?

In order to install solar panels safely and without a permit, you need to be aware of the ‘no go zone’. This is the distance from the eaves where it is best not to install solar panels.

The government indicates that the prohibited zone must be the same size as the height of the solar panels. For example, if the highest point of the panel is 50 cm above the ceiling, the distance to the edge of the ceiling must also be (at least) 50 cm

Installation of solar panels on a flat roof

Solar panels are installed on a flat roof on triangular frames. These frames are placed on the roof and then weighed. As a result, the panels do not blow away during a storm. Weighting is usually done with tiles or pebbles.

There are two types of mounting frames:

open frame

An open frame is usually made of metal, such as aluminum. The great advantage of an open mount frame is that more wind will blow under the panels. This provides cooling, which means the panels generate more electricity.

The downside of an open mount frame is that the solar panels catch more wind during a storm. Therefore, open frames should be weighted better.

closed frame

A closed frame is usually made of plastic. The advantage of a closed mount frame is that the solar panels catch less wind during a storm. Therefore, the closed squares have less weight than the open squares.

The downside of a closed mount frame is that the solar panels are less cooled by airflow. As a result, they generate less electricity than solar panels in an open frame on hot days.

shadow on the ceiling

Shading is also an important aspect for solar panels on a flat roof. There may be obstacles around your house or on the roof, which can cause shadows on the roof. There are two ways to solve the shadow problem.

Prevent shadows with investors

There is a special conversion technique that can greatly counteract the shadow effect. By placing an individual inverter per panel, each panel is controlled individually. If there is shade on one of the panels, only that panel provides less power, rather than the entire installation.

The right choice for an investor can shorten the payback time by  years  . 

Place solar panels avoiding shadows

Some people have a large ceiling at their disposal, which gives them more freedom in the placement of the panels. In that case, you can choose to avoid shadow spots on the roof by strategically placing solar panels. Be aware of obstacles that can grow, such as trees.

Advantages of solar panels on a flat roof.

The advantages of flat roof solar panels are:

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