German utility RWE AG (RWE.XE) Tuesday said it swung to a net loss in the second quarter of 2011, driven mainly by additional costs related to Germany’s decision to exit nuclear energy by 2022 and a tax on nuclear fuel.

The early closure of reactors also resulted in an earnings shortfall, because RWE sold forward the electricity that should have been produced in its two shuttered reactors. To meet its supply obligations the company now has to produce that electricity in more expensive plants or buy power on the market, both of which hurts generation margins.