How does the MyDualSun sizing block work?


How many panels to install according to the geographical area?

➡️ In the northern half of France, above Lyon/Bordeaux (limit of the 45th parallel), we recommend 1.5 panels/person depending on ECS needs.

➡️ In the southern half of France, below Lyon/Bordeaux (limit of the 45th parallel), we recommend 1 panel/person depending on ECS needs.

Our sizing software MyDualSun will give you all the information you want based on the specifics of your project.

The tool recommends a certain number of DualSun SPRING hybrid solar panels that can meet your hot water needs. You also have the possibility of adding DualSun FLASH photovoltaic solar panels to increase your electricity production (to optimize the self-consumption bonus for example) and your energy autonomy.


What is the need for Domestic Hot Water per person per day? At what temperature?

The daily need for domestic hot water per person is on average 50 liters at 40°C, or around 35 liters at 55°C for cold water of 16°C (average annual temperature in France).

Know that on our solar simulator MyDualSun, the simulations are carried out with these sizing ratios. Therefore, if you indicate a number of people in your household of 4. The simulation software will dimension the number of SPRING panels required that can provide 200L/day of hot water at 40°C.


How does the MyDualSun software determine the maximum number of panels installable on my roof?

In order to determine the maximum number of panels that can be installed on your roof, our simulation software MyDualSun is based on the length and width of the selected panel.

Each panel has specific dimensions that you can find in their technical sheet, available here: Technical Documents 

We must also distinguish the shape of the roof:

  • roof terrace,

  • rectangular roof

  • triangle roof

The surface area of ​​the panel is then compared to the surface area of ​​your roof, taking into account the necessary spacing between panels.
In the case of a roof terrace, we calculate the spacing between each panel according to the degree of inclination of your roof so that there is no shadow on the panels in the worst angle of inclination of the sun : the winter solstice. Then we apply a safety distance around the edges of your roof.

We compare the maximum number of panels installable in portrait and landscape and we keep the highest number of panels to offer it to you.


> To go further, we detail the calculations carried out by our sizing software below:

  • Lr: roof length

  • lr: roof width

  • Lp: length of the DualSun panel

  • lp: width of the DualSun panel

  • a: inclination of the panels on the roof terrace

  • b: angle of the sun during the winter solstice at noon

  • e: spacing between the frames of 2 successive panels. The value used by default is 2 cm.

  • x: spacing between 2 rows of panels on a flat roof

  • s: buffer margin between the edge of the roof and the 1st panel on a flat roof. The value depends on the roof, the parapet and the certifications of the installation systems. You can consult our certification ATEC SOPRASOLAR FIX EVO. Here we will take the value of1 meter recommended by Soprasolar.

  • Nmax: maximum number of panels installable

  • B2: small length in the case of a trapezoidal roof


On the roof terrace

Translation : 

  • Position du soleil au solstice d’hiver à midi: Sun position during winter solstice at noon

  • Panneau rang n: Rank n Panel 

  • Toit: roof

  • Toit vue du dessus: Roof from above

  • Lp: portrait length

  • Lp: landscape length


The algorithm is as follows:

In order to calculate the spacing between 2 rows of panels on a flat roof, let's use the following formulas:

  • x = (1+sotan(b)).body(a).lp  in landscape

  • x = (1+sotan(b)).body(a).Lp  in portrait

We then calculate the number of panels that can be installed on your roof by rounding down to the lowest whole number in the formula below:

  • Nmax = Lr - 2.sLp + e .

Rectangular sloping roof

We calculate the number of panels installable on your roof by rounding down to the lowest whole number in the formula below:

  • Nmax = Lrlp + e . lrLp + e in portrait

  • Nmax = LrLp + e . lrlp + e in landscape

On a sloping triangle or trapezoid roof

The calculation is quite similar for the 2 types of roof. We must think of the trapezoid as being included in a triangle.

tan(&) = 2.lrLr.tOf   for an isosceles triangle roof

tan(&) = 2.lrLr-B2  for a trapezoid roof

The algorithm is as follows:

  • We are trying to fit a panel of width lp onto the roof at the bottom left, taking into account a safety margin.

  • As long as a panel fits, add one to its right

  • As soon as we can no longer fit in, we move to the top line.

  • And we start again


How is the percentage and volume of antifreeze calculated for an installation and in the MyDualSun software?

The antifreeze used is glycoled water. It is injected into the hydraulic circuit of a hybrid solar installation. It helps prevent freezing in the pipes.

The volume of glycoled water is the sum of the volume of the piping, the volume of each hybrid panel and their connections:

In figures, you can find on the technical sheet of our SPRING panel the volume of the exchanger: 5L per panel. As well as the volume de la liaisonDual QuickFit portrait: 0.27 L or landscape 0.45 L.


> To go further : What is MyDualSun ?