Last Friday (20.04.15) we experienced a partial eclipse of the sun in Germany.
There were some headlines in online magazines saying, that there might be some issues with the electricity supply since the eclipse will impact many solar power plants. And in Germany there are quite many of them. According to Wikipedia, in 2013 there was around ~35GW installed solar power in whole Germany.
After the eclipse, I asked a friend if he could send me some data from his parents solar power system.
Here we see a drop in power starting at around 10 a.m down to 2.6kW at around 10:30 a.m.
Just before noon, the power maximum was reached of around 7.8kW.
So the eclipse reduced the max. power from 7.8kW to 2.6kW, that is only one-third of the peak power.