"If Russian gas stops completely, the current grid infrastructure is not sufficient as we will have to supply eastern Europe and Austria via Germany," said Birnbaum, who also heads the Eurelectric industry lobby, in a panel discussion during the German BDEW utility association's annual congress.

"And only a bigger and more flexible power system can cope better with the intermittency of renewables," he added.

(Reporting by Vera Eckert and Riham Alkousaa, editing by Miranda Murray)