European solar plants generated 52 TWh in June and reached a record 55 TWh in July. Solar output covered roughly one-quarter of electricity consumption in both months. The higher generation arrived during a period when extreme temperatures pushed demand up across parts of Europe.
Temperatures exceeded 40C, increasing air-conditioning demand. At the same time, the heat worsened hydrological conditions. Drought constraints also affected power supply, with hydropower production between May and July falling to its lowest level for that three-month period in at least a decade.
Hydro and nuclear constraints during low river flows
Nuclear generation faced additional vulnerability from high temperatures and low river flows. Both reactors at Romania’s Cernavoda nuclear plant were taken offline as Danube levels fell. Hungary reduced output at Paks and temporarily shut several units.
On 12 July, France had around 29 GW of unavailable nuclear capacity. Scheduled maintenance accounted for much of this figure, while environmental restrictions and forced outages were estimated to have affected as much as 11 GW. These outages contributed to a tighter operating balance during the summer period.
Heatwave price spikes and evening market tightening
Wholesale prices tightened quickly as supply conditions moved closer to demand. During heatwave periods in late June and early July, average Hungarian electricity prices were 119% above comparable days from the previous week. France rose 44%, while Italy increased by 13% and Spain by 7%.
Solar generation reduced scarcity pressure during daylight hours, but system conditions tightened after sunset. Prices rose sharply during early evening hours as photovoltaic output disappeared while cooling demand remained elevated. The shift highlighted the growing value of flexibility resources during the evening transition when renewable output declines fastest.
Flexibility needs as solar output falls after midday
The summer period showed how solar can protect the midday market from scarcity as renewable output stays available through daytime. Storage, hydro and other dispatchable capacity became more valuable during the evening transition. This timing effect aligned with higher evening demand for cooling after temperatures remained elevated.
