Speaking to BBC World News in an interview that will air on Friday, Gates said he did not feel guilty about being wealthy provided he “takes the money and makes sure it goes back to society in a highly impactful way.”

Gates, whose philanthropic endeavors focus on various issues including public health and climate change, has been accused of hypocrisy in recent years over his continued use of private jets. In the BBC interview he defended using his fortune to fly privately, even as he continues to be a prominent voice in the fight against climate change.

“I’m comfortable with the idea that not only am I not part of the problem by paying for the offsets, but also through the billions that my breakthrough energy group is spending, that I’m part of the solution,” the Microsoft cofounder said.

He noted that his “fanatical” work ethic had helped him build up his vast fortune, which is estimated to be worth around $115 billion, according to Bloomberg—making him the fourth richest person in the world.

“Working for me was a guaranteed way to make tens or hundreds of millions of dollars,” he joked. “And to work on some of the most interesting and amazing things possible.”

Asked if he lived a frugal lifestyle—aside from his use of private jets—Gates implied that he doesn’t splash out on flashy, expensive items.

“I don’t have a gigantic closet,” he said. “I don’t wear jewelry.”

However, he also suggested that he wasn’t obsessively thrifty.

“When I’m unwrapping a present, I don’t take the wrapping and fold it up and use it again,” he explained. “My grandmother never threw a paper bag [away] in her life or any string on a package, so by her standards, I’m crazy—I just take the bag, and I put it in the garbage.”