One of America’s oldest and coldest cities may be squandering energy in prodigious amounts, a new study finds. In a 1-year period beginning in 2012, roughly 3% of the gas delivered to the greater Boston area was released into the air, the report says, three times more than previous annual estimates. The emissions are a threat to the climate and a sheer waste of money. And it raises the question of whether other cities share Beantown’s newly uncovered methane problem.

Fortunately, methane emissions can be reduced relatively cheaply, compared with emissions from coal plants or cars. “There’s an opportunity to deal with emissions from methane because they come from inefficiencies in the system that we can fix,” says Kathryn McKain, a graduate student at Harvard University who led the study. But first you have to find the leaks, she says—not easy in a tangle of buried pipes, storage facilities, and landfills that may be releasing gas.

Natural gas emits about half as much carbon dioxide as coal when it burns, making it an appealing alternative to coal for generating electric power. But there’s a hitch: If methane, the main component of natural gas, leaks out of the energy system before it burns, it rapidly warms the atmosphere. (Depending on how you count, methane’s greenhouse warming potential is 34% to 86% higher than CO 2 .)

Earlier studies have hinted that Boston and other cities might be leaking large amounts of methane into the atmosphere. (Just last week scientists found methane emissions in the Los Angeles area roughly 61% higher than previous estimates.) So in 2012, McKain and other scientists set up monitoring stations at four locations in the metropolitan region: two in the city center—including one on a skyscraper—one on the coast, and one in a forest 50 km from downtown, just outside the study region.

The instruments showed more methane in the air in the city than in the outskirts. With the help of a regional weather model, the scientists were able to estimate how much of that increase came from sources of methane inside the study region rather than wafting in from elsewhere.

The main finding: Between 2.1% and 3.3% of the methane in Boston’s air comes from local leaks—three times more than researchers had estimated from an inventory of known methane sources in the study area. All told, the leakage amounts to 0.17 cubic meters of methane per person per day. “We knew that Boston's aging infrastructure leaked natural gas, but these measurements suggest a higher number than indicated by national and state level greenhouse gas inventories,” says Peter Huybers, a scientist at Harvard who didn’t participate in the study.

According to the new study, to be published tomorrow in the Proceedings of the National Academy of Sciences, the squandered gas has a value of $90 million—a financial loss for gas distributors and consumers alike. Federal and state officials have already taken steps to reduce such losses: Last year, the state of Massachusetts passed a new law that strengthens rules on monitoring and repairing leaks, and the Environmental Protection Agency has proposed new rules to further stem methane emissions across the country.

Environmental advocates are applauding those measures, because the Boston study may point to a nationwide problem. Recent studies of natural gas production facilities in Utah, for example, have found emissions as high as 9% of gas recovered from wells.

“If we add [the Boston emissions] to the emissions that we are getting in some production regions, the methane emissions due to natural gas [nationally] could be quite high,” says Colm Sweeney of the National Oceanic and Atmospheric Administration in Boulder, Colorado. Sweeney, who led the Utah study, says that “more work needs to be done to make sure Boston is not an outlier.” That research could include more sampling of urban industrial facilities that use methane or even dispatching drones to sniff out methane from above.