Pumps that supply water to Phoenix and Tucson are powered by the station.
The Central Arizona Project spent $81.2 million last year on power from the facility and made $12 million selling the surplus.
Natural gas would have saved about $26.5 million.
"Twenty-six point five million really sticks in my craw," said Terry Goddard, a project board member and former Phoenix mayor and state attorney general. "We are subsidizing or moving in a losing proposition. We should do something to stop that if we possibly can. Are we the dog or the tail, the windshield or the bug?"
Other board members were concerned about the volatility of natural gas prices.
Converting the Navajo Nation facility to a natural gas plant would be inefficient and costly, said Ron Lunt, director of operations and engineering for the Central Arizona Project.
"The problem with NGS (the Navajo Generating Station) is the location of it and the nearest gas line is roughly in the Flagstaff area," Lunt said.