Heavy solar supplies and prospects for weak demand cut European spot power prices on Friday as the region anticipated a long weekend due to the Whitsun holidays on June 8 and 9.
Average daily solar output in Germany will be around 9.5 gigawatts (GW) on each of the next three days, Point Carbon data showed.
The German met office DWD wrote of "mid-summer heat" being on the cards as southern air flowed into the region, bringing Saharan air and high sunshine. Germany has 36 GW of installed solar capacity.
The maximum daytime temperature may break above 30 degrees Celsius on Saturday and the following two days.
The German baseload power contract for delivery on Saturday was 25 euros ($34) a megawatt hour, down 7.5 euros from Friday, Sunday traded at 19 euros and Monday at 21 euros.
The next working day, June 10, was 33.75 euros. France followed a similar pattern, with Tuesday at 32.05 euros, up 2.70 euros from Friday and weak prices in between.
Consumption was indicated to drop by around 7 GW from normal weekday levels during the three-day break and by up to 10 GW in France, according to Point Carbon.
Along the forward curve, power prices eased, reflecting weaker coal, gas and carbon prices.
The Cal '15 baseload power contract for next-year delivery in Germany was down 5 cents day-on-day at 34.15 euros and the equivalent French benchmark contract fell by 10 cents to 41.75 euros.
German transmission firms said they are well prepared for dealing with a massive solar influx on the networks which require additional staffing to handle load flows and, in case of overload, reduction measures.
One challenge is that flows towards the Czech Republic and Poland will have to be kept up although German grids are running in weekend mode, said eastern German operator 50Hertz. Those countries have different holiday schedules and markets there will be open on Monday.
($1 = 0.7345 Euros)
(Reporting by Vera Eckert, additional reporting by Tom Kaeckenhoff, editing by David Evans)