The tax of €0.0205 ($0.023) per kilowatt hour of produced electricity would affect some 100,000 solar plants of small- and medium-sized companies, farmers and cooperatives, the BSW estimates. Only very small rooftop PV would be exempt.

"The electricity tax had been introduced to accelerate the Energiewende, not to slow it down," says BSW managing director Carsten Körnig.

He adds that the tax would render a great part of the solar electricity market unviable.