The Northeast’s cap-and-trade program generated $1.4 billion in net economic benefits over the past three years for nine states, even though electric power plants in the region took a $350 million hit to their revenues, according to a report released April 17.

Natural gas, oil, and coal plants experienced a revenue loss of $940 million over three years because they are required to purchase one carbon allowance per ton of carbon emissions under the Regional Greenhouse Gas Initiative requirements, the Analysis Group’s report said.

On the other hand, nuclear, hydro, wind, solar, biomass, and pumped storage plants had a $590...