Bill Weihl, Google's 'green energy czar', is leaving the company this week after steering its clean energy efforts for almost six years.
Weihl had a hand in almost all of Google's green initiatives, including its research and investments in clean technologies, and its efforts to reduce energy consumption in its data centers. He has also been a frequent public speaker for the company.
Weihl's last day at Google will be Tuesday, a company spokesman said.
"Bill has catalysed thinking and action about clean energy at Google and beyond, and has played a crucial role in developing our approach to sustainability," said Urs Hoelzle, Google's senior vice president for technical infrastructure.
Google didn't say why Weihl is leaving or what he plans to do next, and he couldn't immediately be reached for comment. "It's time to move on and find something new," he told the website Fresh Dialogues, which first reported the news.
Weihl played a "unique role" in that he bridged several different teams at Google, the company said. Hoelzle will continue to lead its data centre efficiency programme, and Rick Needham continues to lead its clean energy investments.
Google didn't say if it would appoint a new energy czar.
Weihl joined Google in 2006. He was previously CTO at Akamai Technologies and earned a doctorate in computer science from the Massachusetts Institute of Technology. He is a vice president and co-chairman of the Climate Savers Computing Initiative.