Solar energy: Inexhaustible – including in Switzerland

How it works

Photovoltaics is based on the ability of certain materials to convert light from the sun directly into electricity. The underlying physical principle is called the photovoltaic or photoelectric effect.

Simply put, solar energy works like this: While light falls on the solar cells, they generate direct current from it. This means that light energy is converted directly into electrical energy. The individual solar cells are interconnected to form larger solar modules. The direct current generated is converted into alternating current by the inverter and can thus be consumed directly on site or fed into the power grid.

Do you want it in more complex terms? Here you go:

So-called semiconductors are used in solar technology like they are also used in the manufacture of computer chips. They owe their name to the fact that they can act as an electrical conductor and a non­conductor. ln a solar cell, the non-conductive material becomes a conductor when the electrons are released from the non-conductive crystal compound by the absorption of a photon (sunlight consists of these countless tiny energy carriers). The kinetic energy that they absorb forms the generated current. This is direct current, which is converted into alternating current by an inverter to make it suitable for the power grid.

Our solar energy

Switzerland is facing a major challenge: by 2050, there will be a shortfall of around 50 terawatt hours of electricity per year. We therefore urgently need to develop more renewable energies in order to achieve the energy transition and ensure a high level of supply security. Solar energy can make an important contribution to the power mix. Axpo's solar offensive aims to implement around 4,200 solar projects in Switzerland by 2030 with a capacity of more than 1.2 gigawatts in the mountains and on the midlands. This is enough to meet the annual energy needs of more than 300,000 Swiss households.



solar power to be developed by 2030


solar projects

are to be realised by 2030


million households

can be supplied with it per year

We are the expert in large-scale solar plants

With Axpo subsidiary Urbasolar, we are active across the entire solar value chain.

PV on office buildings, industrial roofs, car parks, shopping centres, greenhouses and on open spaces are our speciality.

Axpo aims to develop ten gigawatts of solar energy in Europe by 2030.

Solar energy from A-Z

Photovoltaics and solar energy have many different aspects. You will find a quick summary to a few important keywords below (FAQ).

The six most important answers about solar power

A solar cell is about the size of the palm of your hand and consists of two layers that are two to three tenths of a millimetre thick. Today, most solar cells are made of silicon. Their basic material, quartz sand, is available in sufficient quantities on earth - and silicon is considered environmentally friendly.

There are two types of solar cells: Crystalline and amorphous. Crystalline cells account for the largest share of global production. Monocrystalline solar cells are manufactured from pure silicon, which is withdrawn from a silicon melt in a time-consuming and costly process, pressed into bars, and then cut into discs up to 12 centimetres in diameter. All atoms are aligned equally in the monocrystal. The blue to black cells, which also come in different colours if desired, harvest up to 24 per cent of the solar rays in the Iaboratory; in practice, efficiency is 16 to 20 per cent.

Multi-crystalline solar cells consist of industrially produced polysilicon, and their production is significantly less expensive than monocrystalline solar cells. They are bluish in colour and their efficiency in practice is between 11 and 14 per cent.

Amorphous solar cells are less expensive and suitable for simple applications such as a garden fountain or on large house facades. In amorphous solar cells, the electricity generating layer is steamed onto a glass plate. The atoms are no Ionger deposited in a crystal structure, but in a disorderly (amorphous) manner instead. Relatively little silicon is needed for this process, which lowers the price. ln comparison with the 0.2 to 0.3-millimetre thick crystalline cells, these so-called thin-layer cells measure only 0.01 to 0.05 millimetres. The cells are brown or anthracite and have an efficiency of 6 to 10 per cent. On gloomy days, amorphous cells deliver more electricity than others - but their efficiency drops over the years.

When the sun shines, solar panels produce electricity. Logical, isn’t it? But even on less clear days, solar cells can produce electricity, although not at full capacity. This is comparable to our skin, which reacts to solar UV rays even when it is cloudy. Around 75 percent of the electricity generated by conventional solar systems installed in the lowlands is generated from May to September. What’s more: Solar plants do not produce electricity during the night. ln contrast to base load energy from hydropower or nuclear power, photovoltaic power is therefore only moderately predictable and controllable.

By the way: The share of photovoltaics in the Swiss electricity mix in 2018 was 1944 GWh, which corresponds to around 2.9 per cent.By the way: the share of photovoltaics in Swiss electricity production in 2018 was 1944 GWh, which corresponds to around 2.9 percent.

A typical solar panel (one square metre in size) made of commercially available silicon can generate an average of 180 W on a clear, sunny day in Switzerland. That's enough to run a Iaptop computer. A solar system consisting of several panels with a size of 20 square metres produces around 3600 kWh of electricity per year. In comparison: An average Swiss household consumes between 4500-5000 kWh of electricity per year.

As a general rule, the output of solar modules essentially depends on the amount of sunlight (global radiation/geographical location), on orientation (the more precisely the photovoltaic system is positioned at the optimum inclination angle to the south, the higher the yield) or on shade (from trees, chimneys, etc.). But of course the quality of the solar cells also has a significant influence on the overall performance.

A solar park is a large number of solar modules that are installed on fields or other large surfaces and feed the generated electricity into the grid. Sometimes they are referred to as solar farms or open space solar plants. ln a solar park, the solar modules are installed on approximately 3-metre high mounting systems, which are placed into the ground like fence posts. Rows of these mounting systems would be a typical feature of a solar park. Solar parks can be of any size. About 1.6 to 2 hectares of land are required for every megawatt (MW) of installed solar modules (around 4000 modules per MW).

Studies show that up to 67 TWh of electricity could be generated on rooftops and facades in Switzerland. This corresponds to around 110 per cent of annual electricity consumption in Switzerland. If other infrastructures (car parks, reservoirs, noise barriers) and other open spaces, such as those in already developed Alpine regions, were to be covered with solar panels, there would be an additional potential of 25 per cent. The sun could therefore become a major factor in Switzerland's energy supply. However, politicians would have to create incentives for this, i.e. design the market and the framework conditions in such a way that companies are prepared to make the necessary investments - also for large-scale plants. In addition, a strong expansion of photovoltaics requires large storage facilities, which do not yet exist, as well as grid expansion and grid reinforcement, especially at the lowest Ievel.

How much does electricity produced from photovoltaics cost? Thanks to increasingly cheaper solar modules, the production costs for solar energy are continue to drop. They are between 8 and 28 centimes/kWh depending on the size of the system. For comparison, the production costs for nuclear power plants are between 4 and 7 centimes per kWh – for large-scale hydropower they range between 4 and 9 centimes per kWh.

ln addition, the costs per kWh of electricity produced also depend to a large extent on the location, i.e. the local sunshine duration/radiation. In a normal year, the sunshine duration in Lugano is around 2100 hours, while in Glarus it is only around 1200 hours. Accordingly, more or less solar energy can be produced, which naturally has an impact on costs.

Experience solar energy

Smart Energy Lab

Solar energy is an important component of the electricity system. Under the Energy Strategy 2050, power generation from sun and wind is becoming more and more important. 

The Smart Energy Lab explains in simple terms how the system functions and what role solar energy plays as a whole. More information on the permanent exhibit at Umwelt Arena in Spreitenbach.

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