How to estimate the yield and production of your future solar panels

Photovoltaics is certainly the most accessible renewable energy, financially and technologically, to the general public. However, it conveys a lot of fantasies and sometimes sees itself oversold. To help you see more clearly, we suggest that you understand and calculate the energy yield of your photovoltaic project.

Despite the return to favor of nuclear power, renewable energies are not to be discarded, far from it. And in this field, photovoltaics is certainly the energy most accessible to the general public. However, behind the flattering figures of the energy capacities of solar panels hides a slightly more complex reality. Let’s clear all this up a bit so that you can make a quick estimate of the energy yield of your future solar panels.

What factors affect the efficiency of a solar panel?

Solar panels are surfaces that will convert solar energy into electricity. There are several photovoltaic panel technologies with different yields. Two dominate the market:

  • monocrystalline silicon panels, dark in color: they offer on average an efficiency of 18% to 19%;
  • those in polycrystalline silicon, blue in color: their average efficiency is less efficient (12 to 15%), but they are less expensive to purchase.
Source : Unsplash/Manny Becerra

The technology of your future solar panels is therefore the first element that will affect your electricity production. But it is not the last and many other parameters come to influence it.

Each panel has a Maximum power (Pmax on the technical sheets) which is expressed in Watt Peak. It corresponds to the maximum electricity production that a solar panel can generate under “optimal” which are :

  • The level of sunshine at the place where the panels will be installed and which is measured in Watts/m². Optimal sunshine is 1000 Watts/m², which corresponds to bright sunshine at noon and without an ounce of cloud.

  • An outside temperature of 25° is considered optimal, but it is not so simple. If the solar panel does not have sufficient ventilation at the back, it can quickly “heat“. This will have the effect of reducing its performance significantly. Paradoxically, you can therefore find yourself with greater energy efficiency in winter than during heat waves.
  • The inclination of the panels is another essential point, which must be adapted according to the latitude of the solar panels. To simplify, an optimal inclination in the south-east of 30°, 40° in the north and around 35° in the center of France.
  • Finally, you can have the best panels in the world, the best sunshine, if you place your solar panels in a shady area, you might as well not.

Attention, without meeting all these conditions, the installation of solar panel remains interesting. Above all, it will be two to three times faster to make a profit on the Côte d’Azur than in Dunkirk.

How to estimate the production of your solar panels

Your electricity production depends on the performance of your solar panels, their surface and finally the solar power received. The latter varies according to your latitude and the number of hours of sunshine per year. France can be divided into four zones:

  • North of France and Paris region with 1400 to 1600 hours of sunshine per year;
  • Central regions with 1600 to 2000 hours of sunshine per year;
  • The southwest with 2000 to 2400 hours of sunshine per year;
  • Finally, the PACA and Corsica regions with 2400 to 3000 hours of sunshine per year.

Interesting figures, but which are not very enlightening if one does not know the solar power received in his area of ​​residence. The map below gives an idea of ​​the photovoltaic energy potential of your department.

However, for the future energy producer that you are, what interests us most is the average level of production in your region.

As a reminder :

  • The watt (W) is the unit of measurement of energy power.
  • The watt hour (Wh) is the unit of measurement used to indicate the amount of energy produced by the panels in one hour.
  • The peak power is the power of the photovoltaic modules expressed in Watt Crete (Wc). This is the maximum power that the solar panel will produce under optimal conditions.

What interests you the most is above all the solar production yield, which corresponds to the production of electricity (which is expressed in Wh), per month or per year for 1 Watt Peak (Wp) installed. This kWh produced/kWp ratio is therefore expressed in Wh/Wp and there are four major production zones for France.

The performance of solar panels // Source: Total Energies

  • Zone 1: here we mainly have the DOM-TOMs with a solar yield of 1418 Wh/Wp.
  • Zone 2: the second most favorable zone in France for the installation of photovoltaic panels includes the Provence-Alpes-Côte d’Azur, Corsica and Occitanie regions with yields of around 1150 Wh/Wp, 1148 Wh /Wp and 1145 Wh/Wp.
  • Zone 3: it includes the central regions of France, with an annual solar yield ranging from 1095 and 1115 Wh/Wp.
  • Zone 4: this zone groups together the regions of the north (Ile-de-France included), the extreme west and the east of France. Their solar yield is between 1007 and 1081 Wh/Wp.

Here is a small table for each region of France:

RegionsAverage return last monthPrevious 12 month return
Auvergne-Rhone-Alpes94 Wh/Wc
Burgundy–Franche-Comte100 Wh/Wc1063 Wh/Wc
Brittany112 Wh/Wc1055 Wh/Wc
Centre-Val-De-Loire105 Wh/Wc1038 Wh/Wc
Corse1094 Wh/Wc
DOM-TOM1436 Wh/Wc
Great East95 Wh/Wc1041 Wh/Wc
Haut-de-France94 Wh/Wc979 Wh/Wc
Ile-de-France95 Wh/Wc978 Wh/Wc
Normandie110 Wh/Wc1026 Wh/Wc
New Aquitaine116 Wh/Wc1122 Wh/Wc
Occitania114 Wh/Wc1167 Wh/Wc
Pays de la Loire110 Wh/Wc1096 Wh/Wc
Provence-Alpes-Cote Azur132 Wh/Wc1266 Wh/Wc

Source : BDPV

Now that you have this information, it becomes easier to estimate the production of an installation. Thus, if you are planning a 3 kWp installation and you live in Brittany, you will produce approximately:

Ratio kWh produced/kWp (1,055 kWh/kWc) x Installed peak power (3 kWc) = 3 165 kWh/an.

Many tools can simplify your estimates. We have selected two from associations dedicated to the promotion of photovoltaics:

Now you have all the tools to better understand the ins and outs of photovoltaic energy production. You can get a more precise idea of ​​the production that your future installation of solar panels will be able to generate.

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Source: Frandroid by

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