Elon Musk said on Monday via Twitter that people need to work from around 80 to over 100 hours per week to “change the world.”
“There are way easier places to work, but nobody ever changed the world on 40 hours a week,” Musk said, referring to the four companies — Tesla, SpaceX, The Boring Company, and Neuralink — where he serves as CEO.
When asked by a Twitter user about the number of hours one needs to work each week to “change the world,” Musk replied that it can range from around 80 to over 100.
“Varies per person, but about 80 sustained, peaking above 100 at times. Pain level increases exponentially above 80,” he said.
Tesla declined Business Insider’s request for comment. SpaceX and The Boring Company did not immediately respond to requests for comment.
Musk said in an interview with Recode published in November that he was working 120 hours per week while “everyone” at Tesla worked 100 hours per week at times this year as Tesla ramped up production of its Model 3 sedan. He suggested the long hours was necessary for Tesla to survive.
“There wasn’t some other way to do this,” he said.
Tesla employees have described working long hours to Business Insider. Some employees have said the hours are excessive, while some have said they prefer to work 70 or more hours per week.
This article originally appeared on BusinessInsider.com.