Exports of U.S. liquefied natural gas may double prices for the fuel by 2040, but rising output and better trade balances will soften the blow to consumers, according to a study commissioned by the Energy Department.

There’s an almost 50 percent chance of gas reaching $5 to $6.50 per million British thermal units over the next two decades, the study shows. But shipments of LNG overseas will boost the U.S. economy, while higher output will meet most of the export boost, according to the report, conducted by NERA Economic Consulting.

The U.S. is already shipping record amounts of super-cooled natural gas overseas as production from shale basins surges. The nation is now a net exporter of the fuel for the first time since the 1950s, putting the U.S. on course to rival Qatar and Australia for global LNG dominance in the next five years as new Gulf Coast terminals start up.

U.S. gas futures have averaged about $2.90/MMBtu over the past year amid ample supply. Some groups, including several Democratic lawmakers and manufacturers, have argued that a jump in LNG exports would send prices sharply higher, hurting consumers.