The move comes as the energy group presses ahead with plans to list Plenitude on the Milan bourse in what is likely to be one of Italy's largest initial public offerings this year.

Plenitude, which currently has 10 million customers, said it would initially acquire 25% of EnerOcean S.L. but did not disclose financial details.

Plenitude plans to grow its renewable energy capacity to more than 15 gigawatts by 2030 from 1.2 GW this year, mainly in solar.

But the company is also interested in growing its offshore wind business and is looking to Norway, the United States and Italy.

(Reporting by Stephen Jewkes, editing by Giulia Segreti)