The environmental campaigners said that windfarms are "often stopped in peak production periods to give priority access" to electricity generated by nuclear reactors and coal-fired power stations.
Greenpeace researchers said that solar energy in Europe's south and wind energy from the north could supply 68 percent of the 27-nation EU's electricity needs in 2030 and 99.
5 percent by the middle of the century.
However, the group claimed that would require governments to change policy tack and favor investments in green energy to the tune of 94 billion dollars by 2030.
"It's a question of choice," said campaign figurehead Jan Vande Putte.
Renewables produced 16.1 percent of German electricity needs in 2009, more than double the total six years earlier, according to the German federation of renewable energy producers.
Greenpeace is trying to influence the debate in the run-up to a February 4 summit of EU leaders representing half a billion people.