Solar power prevents Swiss electricity shortfall despite drought

Solar power has so far prevented an electricity shortfall in Switzerland despite exceptionally low river levels reducing hydropower output, SRF reports.

Weeks of drought without significant rainfall have left small rivers reduced to a trickle. Larger rivers, including the Aare, Rhine and Rhone, are in some places carrying less water than at any time since measurements began. Run of river hydropower plants are therefore producing significantly less electricity than the long term average.

Repower, an electricity provider from the canton of Graubünden, told SRF that production at its hydropower plants was about 25 percent below the long term average from May to July because of low water inflows. Valais energy company Forces Motrices Valaisannes said low winter rainfall had left the snow cover below average, resulting in less snowmelt and lower production at run of river plants during the same period.

Alpiq, an energy company based in Lausanne, reported very low inflows at its run of river plants, particularly those along the Aare. It put the decline at around 15 percent compared with the long term average.

Switzerland is also currently without Beznau I and Beznau II, two nuclear power plants. Their operator, Axpo, shut them down because the Aare is too warm, not because of low water levels. The plants use river water for cooling, but the water discharged after the process must remain below certain temperatures to protect animals and plants.

At the same time, the many hours of sunshine have boosted solar generation. The substantial contribution from solar plants this summer is mainly due to the large expansion of photovoltaic capacity since the outbreak of the war in Ukraine, SRF reports.

The Swiss Federal Electricity Commission, ElCom, told SRF that solar power is currently providing an important buffer against the country’s unfavourable hydrological conditions. Without the expansion of photovoltaic capacity in recent years, Switzerland’s electricity balance would be more strained, it said.

Solar power is helping conserve water in pumped storage reservoirs. That water can then be used mainly before sunrise and after sunset, when solar plants are not producing electricity. Without the additional solar generation, Switzerland would probably have to use more reservoir water, import more electricity or export less, and could face higher power prices.

Looking ahead to winter 2026 and 2027, ElCom said reservoir levels are currently low and are expected to remain below the long term norm at the start of winter. However, the outlook remains uncertain and depends on rainfall in the coming months and how operators manage the reservoirs. Medium and long term weather and precipitation forecasts are subject to significant uncertainty.