The Netherlands is not exactly known for its abundance of sunshine. Yet more and more companies and property developers are opting for large-scale solar power installations on commercial rooftops. A frequently asked question in this regard is whether solar panels still generate enough energy in cloudy weather to justify the investment. The answer is more nuanced than many people expect, and for anyone seriously considering solar energy in the Dutch climate, it is worth understanding exactly how PV systems handle diffuse light.
Solar panels perform differently in cloudy conditions than they do in direct sunlight, but that does not mean they stop working. Modern panels are designed to generate energy even in diffuse light, which is a crucial feature in a country like the Netherlands. In this article, we explain how this works, what you can realistically expect, and which factors influence the output.
Solar panels do not require direct sunlight to generate electricity. They respond to light in general, and more specifically to photons that reach the solar cells. In cloudy weather, sunlight is scattered by clouds and reaches the Earth’s surface as diffuse light. This diffuse light still contains enough energy to activate the photovoltaic cells and generate electricity.
The principle behind this process is the photovoltaic effect: when photons strike the semiconductor layer of a solar cell, electrons are released and an electric current is generated. This occurs both in bright sunlight and on cloudy days, albeit at different levels of intensity. Solar panels without sunlight are therefore not entirely passive; they remain active as long as light is available.
In cloudy conditions, solar panels typically deliver between 10% and 25% of their maximum power, depending on the thickness of the cloud cover. In light cloud cover or thin veil clouds, the output can reach 50% to 70% of the peak power. These are not insignificant amounts, certainly not when it comes to large-scale rooftop installations where hundreds of panels work together.
It is interesting to note that, under partly cloudy conditions, solar panels sometimes temporarily generate more electricity than expected. This occurs when the sun first appears from behind the edge of a cloud and the light is intensified by reflection off the cloud edges. This so-called edge effect is short-lived, but illustrates that the relationship between cloud cover and output is not simply linear. For commercial projects, it therefore makes sense to base calculations on realistic annual averages rather than peak conditions alone.
Not all cloudy days are the same, and the final energy yield is determined by a combination of factors which, taken together, determine the system’s efficiency.
Thin cirrus clouds allow considerably more light through than thick cumulus clouds or a closed layer of stratus. The light intensity on the panel, expressed in watts per square metre, directly determines how much electricity is generated. On a typical Dutch winter’s day with a completely overcast sky, solar irradiance can drop to less than 100 W/m², whilst a summer’s day with partial cloud cover can still reach 400 to 600 W/m².
In diffuse light, the orientation of the panel is less critical than in direct sunlight, as the light comes from all directions. Nevertheless, a suitable tilt angle remains important for water drainage and for optimising the capture of available light throughout the year. For latitudes in the Netherlands, an angle of approximately 30 to 35 degrees is generally optimal.
The efficiency of the solar cells used plays a major role in solar energy generation on cloudy days. High-quality monocrystalline cells perform better in low light conditions than older polycrystalline technologies. In addition, the temperature coefficient is a relevant factor: panels operate more efficiently at lower temperatures, which means that cool, cloudy days in the Netherlands are sometimes more favourable than hot summer weather.
The Dutch climate, with its mix of cloud cover, rain and changing light conditions, calls for panels that not only perform well under optimal conditions, but are also reliable throughout the year. Lightweight PV modules based on thermoplastic polymers, such as Solarge’s SOLO panels, have been specifically developed for large-scale commercial applications where roof load and ease of installation are key considerations.
As these 50% panels are lighter than traditional glass modules, they can be installed on roofs that cannot support the additional load of conventional panels. This significantly increases the number of suitable locations for solar energy projects, including in regions where the roof is already bearing an existing structural load. In the Dutch climate, where installations are exposed to wind, rain and fluctuating temperatures all year round, the robustness of the panel is at least as important as its peak performance on a sunny day. The SOLO panels have been extensively tested against hail, snow and wind, which are typical of the weather conditions regularly encountered in the Netherlands.
For commercial projects, the question is not whether there will be a loss of yield when it is cloudy, but how that loss is systematically offset. The most effective approach combines several strategies which, together, ensure a stable energy yield throughout the year.
Increasing installed capacity is the most direct way to offset the effect of fewer hours of sunshine. By installing more panels than are strictly necessary to meet peak demand, the total annual yield is increased without the need for any fundamental changes to the infrastructure. Lightweight panels make this more feasible both financially and structurally, as the roof load remains limited and installation time is reduced.
In addition, smart monitoring offers a significant advantage. By continuously monitoring the output per panel or per string, anomalies can be quickly identified and rectified. When combined with energy storage or feeding electricity back into the grid, a commercial system can remain economically viable even on less productive days. Solarge provides estimates based on specific project conditions, including location, orientation and shading, so that project partners can gain a realistic picture of the expected annual yield.
Solar energy in the Netherlands is not a gamble on the sun. It is a calculated choice in which performance in cloudy weather, the quality of the panels and the scale of the installation all determine whether a project meets its targets. Anyone who analyses this properly will discover that the Dutch climate is less of an obstacle than it might seem at first glance.
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