The Forum Ökologisch-soziale Marktwirtschaft (FÖS) published a study in October 2017. It shows that conventional energy production causes hidden costs that are not taken into account in the electricity price. The green energy provider Greenpeace Energy, on whose behalf the study was commissioned, speaks of unequal treatment and fraud.

The study showed that the follow-up costs of fossil energy sources are one and a half times higher than the EEG differential costs. If the burdens on the state budget, tax breaks, financial aid, and the overall societal burdens in the context of environmental and health impacts from coal and nuclear power were taken into account, the calculated levy would be 11.5 cents per kilowatt hour in 2017. In comparison, the EEG levy is 6.35 cents per kilowatt hour.

However, the follow-up costs of conventional energy sources, which amounted to 38 billion euros in 2017, are paid for via taxes and levies, in contrast to the 24.5 billion euros in EEG costs. This creates an uneven playing field and justifies the study's call for a national minimum price for CO2 emissions and an end to subsidies for fossil fuels.