By Neetha Mahadevan

FRANKFURT--German energy firm EnBW Energie Baden-Wuerttemberg AG (EBK.XE) said Friday its wind power unit EnBW Windkraft has offered 550 million euros ($611.7 million) for the insolvent wind-power company Prokon Regenerative Energien GmbH.

Last week, the company said it had made an offer for the company and Prokon creditors will make a decision on the offer in early July. They consider EnBW a preferred investor, EnBW had said.

Prokon, which operates 50 wind parks in Germany and Poland, filed for bankruptcy in January 2014, exposing investors to potential losses of EUR1.4 billion and leading German politicians to toughen laws to protect investors.

Write to Neetha Mahadevan at neetha.mahadevan@wsj.com

Subscribe to WSJ: http://online.wsj.com?mod=djnwires