Solar electricity production: making use of roof space

The sun is the largest known energy source. It harbours more energy than humans could ever use, while its rays are freely accessible and can be harnessed directly.

Some of the solar energy that reaches Earth is radiated in the atmosphere or deflected. Even so, the total amount of energy that hits the surface of the earth is still more than five thousand times greater than the amount of energy required by the whole of humanity. In Switzerland, the solar radiation that hits its entire surface area currently amounts to 200 times more energy than the country consumes.

Solar energy is a form of renewable energy, in addition to hydroelectric, wind power, biomass and waste incineration. Photovoltaic systems convert solar energy directly into electricity, and photothermic technologies convert it into thermal energy. Solar electricity production is sustainable and exceptionally low-carbon. It is making a significant, though still expandable, contribution to meeting Switzerland’s climate goals. Solar energy is an increasing part of Switzerland’s electricity production mix. Interest in the technology has also been growing apace among the general public in recent years.

In 2021, photovoltaics covered almost 5% of Switzerland’s annual electricity consumption. Solar power has vast potential: It is predicted that by 2050, around 20% of today’s energy demand could be covered by photovoltaics.

Photovoltaic (PV) systems

In Switzerland, the first photovoltaic systems came into operation in 1982. PV systems chiefly consist of solar modules (or panels), which in turn consist of solar cells. These sometimes wafer-thin cells are produced using semiconductor materials of the sort also used in the manufacturing of computer chips. When exposed to light, they produce electricity that can be used directly on-site (self-consumption) or fed into the public grid in exchange for compensation. The efficiency of the conversion of solar energy into alternating current typically varies between 6 and 20%, depending on the components used.

Amount of sunshine

It is estimated that at least 50% of roofs in Switzerland are suitable for a photovoltaic system. On average, a roof in Switzerland is exposed to 1,800 hours of direct sunlight per year, with an irradiance of 120 watts/m² or more counting as sunshine. In total, this equates to over 75 days of continuous, almost cloudless sunlight per year. In reality, the number of daily sunlight hours in the course of a year varies significantly. However, in Europe, it is not only countries in the south that are capitalising heavily on solar power: the likes of Germany, Belgium and the Czech Republic are doing so, too.

The map shows the proportion of roof space in Switzerland already being used for electricity production with registered photovoltaic systems in relation to the roofs that could be used for solar power production. Facade surfaces have not been taken into account. There is still great potential in the Alps and Ticino in particular