Bob McNair, a transplanted Texan who built an energy empire and earned a fortune that he would spend on an N.F.L. team as well as philanthropic and political causes, died on Friday at his home in Houston. He was 81.

The team he owned, the Houston Texans, announced his death in a statement. A team spokeswoman said the cause was cancer.

A longtime Houstonian, Mr. McNair founded Cogen Technologies, which became the largest privately owned cogeneration company in the world — and then sold the bulk of it to Enron in 1999 for $1.1 billion with an eye toward becoming a National Football League owner.

His aspirations were realized in October 1999, when the league awarded him the franchise that would become the Texans — a move that would return professional football to Houston in 2002, six years after the Oilers had skipped out for Tennessee to become the Titans.