The government is in the process of amending the 2009 Renewable Energy Act, the revised law due to take effect at the start of 2012.
A just-published federal environment ministry review of the workings of the 2009 law proposes decreasing onshore feed-in tariff payments by 2 percent per year. Currently the decrease is set at 1 percent per year.
The new law could also affect two bonuses for developers. A bonus for new wind turbines equipped with sophisticated control systems would be abolished at the start of next year instead of the end of 2013.
Additionally, restrictions would be placed on a repowering incentive for wind developers to replace older turbines with newer and larger models.
If the proposals are adopted into the new law, the bonus would only be applicable to turbines that have operated for a minimum of 14 years and a maximum of 17 years, or to those that were commissioned before 2001.
Speaking about the draft proposals, Hermann Albers, president of the federal wind energy association BWE (Bundesverband Windenergie) said: "If the planned reductions in payments for onshore wind energy are implemented, the federal government's renewables policy becomes a farce.
"The federal environment ministry undermines its credibility if it expounds a swifter growth of renewable energies and at the same time puts the brakes on onshore wind expansion, the most important type of renewable energy, by reducing the feed-in tariff rate."