The ongoing heatwave across Europe has driven up electricity prices on the energy exchange in recent days. However, the increase was caused less by the high demand for air conditioning and more by the heat-related reduction or shutdown of nuclear power plants in France and Switzerland.

In Austria, one kilowatt hour (kWh) of electricity cost 44 cents on the spot market between 8 and 9 p.m. on Tuesday. By comparison, in the cheapest hour of the day—between 12 and 1 p.m., when solar power was abundant—electricity cost just 0.3 cents. The prices were determined during an auction on the electricity exchange Epex Spot SE on Monday.

Hourly electricity prices are generally only relevant for consumers with specific time-based tariffs. These customers can benefit from lower prices during certain hours of the day.

The current European heatwave forced France to reduce output or shut down several nuclear power plants. On Monday, French energy company EDF reported the shutdown of the Golfech plant because the cooling water from the Garonne River had become too warm. In Blayais, production had to be reduced. In Switzerland, operator Axpo shut down one of the two reactor units at the Beznau plant on Wednesday; the second reactor continues to operate at 50% capacity.