It gave no reason for the move, saying only that Crane would assist in the chief executive transition through the end of the year.

NRG shares rose 7% to $11.55 in early New York trading on the news. They had been trading in recent weeks near a 52-week low of 10.52, a third of the $31.13 high during that period.

Under Crane, NRG became one of the country’s largest independent power producers and launched the first major yieldco that included large solar assets – NRG Yield – in July 2013 as an IPO, which opened the floodgates for similar ones by SunEdison and others.

Investors