He is replaced by Elisabeth Borne, who will continue as minister of transport as well as taking on the overarching responsibility for the energy transition.
The loss of De Rugy is particularly bad news for the wind industry after his predecessor, Nicolas Hulot, only stayed in post for just over a year.
Another change of minister "is not very good news for the industry … as change can create instability and put a brake on development," said Marion Lettry, assistant executive commissioner of renewable energy trade body SER.
Crucially, the energy-climate bill, which foresees increased deployment of renewables, is currently going through parliament.
Any delay to that will also impact the long-awaited multiannual energy plan (PPE) slated for final publication before the end of the year. "We hope there will be no change to the programme," Lettry said.
Borne is something of an unknown quantity in the energy sector. She served under Ségolène Royal in what was then the ecology ministry in 2014, and is now minister of transport.
So she has some knowledge of the issues and said in a tweet she is "determined to continue the essential struggle that is the ecological transition".
The industry hopes she will show the same support for the sector as de Rugy, who came with strong environmental credentials.
De Rugy held a position "very much in line with the expectations of the industry" and defended his views strongly both within government and in parliament, Lettry noted.
This was especially true of offshore wind, with the Dunkirk project being awarded under his stewardship, and indications that the offshore targets would be increased.
One possible setback is the downgrading of the ecological transition ministry from second in the government, headed by a minister of state, to a regular ministry.
"It indicates that the government does not give the same weight to energy as previously," Lettry said. She and the rest of the industry will now be working hard to ensure Borne understands the importance of the issues involved.