WASHINGTON

ELECTRIC power plants spew about 40 percent of the carbon dioxide pollution in the United States, but, amazingly, there are no federal limits on utility emissions of this potent greenhouse gas. The Obama administration plans to remedy this situation by drafting rules that would curtail these discharges from existing plants. The president should make sure they are tough. Nothing he can do will cut greenhouse gases more.

By accomplishing this under the executive authority Congress granted him in the Clean Air Act, the president will be stepping in where recent Congresses have refused to go. He did the same thing last August, when he toughened auto emissions standards that will result in a new car fleet that averages 54.5 miles per gallon by 2025, and again last spring, when he proposed rules, restricting carbon dioxide emissions, that will effectively prevent the building of new coal-burning power plants.

Now President Obama should require existing power plants to reduce their emissions by at least one-quarter by 2020. These plants emitted 2.2 billion tons of carbon dioxide in 2011, according to the Environmental Protection Agency, so a 25 percent cut would result in a reduction of more than 500 million tons. This would reduce lung-related illness and premature deaths, slow the accumulation of climate-changing gases in the atmosphere and demonstrate to the rest of the world that the United States was serious about taking on global warming.

To achieve these reductions, the rules should favor making homes, buildings and power plants more energy efficient over the more costly conversion of coal-fired plants to natural gas. (Gas-fired power plants emit half as much carbon dioxide as coal-fired plants. But expanding energy efficiency will reduce electricity demand and eliminate the need for the coal plants. Closing them is better than converting them to gas.) The American Council for an Energy-Efficient Economy says the technology exists now to cut electricity use by one-quarter by 2020 through efficiency alone. Based on the average electricity production of the nation’s large coal-fired power plants, this would allow for the closing of close to 60 such plants across the nation.