Coal mined from the Navajo and Hopi reservations and sent to Mohave Generating Station in Laughlin had been a major source of revenue for the tribes.
The power plant closed in 2005, leaving its owners with credit for sulfur dioxide emissions that could be sold.
The tribes and conservationists went after revenue that the plant's majority owner, Southern California Edison, could generate from the sales.
California utility regulators voted this week to direct that money to renewable energy projects on or off the reservations that would benefit the tribes.
At least $3.5 million sits in a revolving fund from sales of the credits. Future revenue projections are wide-ranging because of the instability of the market.