See: http://www.renewableenergyworld.com/rea/news/article/2013/02/the-future-of-electricity-markets
See Fig. 1. ". . . Germany has seen a surge of renewable energy development since the early 2000s. The consequences of this surge in zero marginal cost power have been clear: electricity prices during the summer on Germany’s spot market are often lowerduring the day than they are during the evening, as the large influx of solar power (approximately 32 GW as of Q4:2012) enters the grid. (The same has occurred with wind power in the north of the country). . . . . . . During the week of May 21, 2012, solar PV produced over 1.1 TWh of electricity, representing approximately 18 percent of total electricity demand in Germany over the same period, and supplying almost 50 percent of instantaneous electricity demand during certain hours of the day." - Jed
