More Methane Is Leaking Than We Thought, It’s Time For Electrification
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More extensive methane leakage

Estimates from the Gas Index model indicate that substantially more methane leakage is occurring from the U.S. natural gas supply chain than is estimated by the Environmental Protection Agency’s Greenhouse Gas Inventory. The Gas Index estimates are higher because they are based on new studies of methane leakage across the gas system, including in production areas and within cities. These new studies often show that components of the system are leaking at a higher rate than previously estimated.


All 71 cities evaluated in the Gas Index have life cycle leakage rates higher than estimated in the EPA’s Greenhouse Gas Inventory, and some cities have leakage rates more than four times higher than the EPA estimate.


By highlighting which cities have the leakiest gas supplies, and which parts of the system are most responsible, The Gas Index highlights where efforts can best be directed for fixing the gas system—and which cities would cut emissions the most by switching from gas-burning appliances to those that run on electricity.

Electricity versus gas

The Gas Index results show significant emissions cuts that can result from buildings switching from using natural gas to using electricity. In residential and commercial buildings, the largest use of gas—and largest use of energy overall—is for space heating. Switching from gas heating to electric heating would cut greenhouse gas emissions in many situations, although not in every case.


The Gas Index estimates indicate that electrifying building heating would lead to emissions reductions in many cases—and that replacing gas heaters with efficient electric heat pumps would lead to emissions cuts in every city evaluated in the Gas Index. Switching building heating from gas to electric heat pumps, while also continuing efforts to make the electricity system cleaner, would lead to even greater emissions cuts.


Shown below are the emissions savings in each city in the Gas Index, if they were to switch homes from gas heating to electric heat pumps, and if cities and states remain on track to achieve their clean electricity commitments. (To see the emissions savings for individual cities, hover over the cities on the map below.)


For more details about this scenario and other scenarios, see the page “Electrification.”

New research finds more gas leaks

The more researchers look, they are often finding more methane leakage from the gas system than previously estimated—in particular leakage occurring within cities.


For example, in a partnership between the Environmental Defense Fund and Google, sensors mounted on cars that drove through many U.S. cities, collecting far more extensive measurements of methane emissions than were available before. Researchers at Colorado State University undertook detailed analysis of those measurements to attribute methane enhancements to leakage from pipelines of particular materials and ages. The study estimated that these pipelines are leaking nearly five times as much as the EPA’s estimate.


The Department of Energy commissioned the Gas Technology Institute to take measurements of leakage from hundreds of customers’ gas meters across the country. Their study, published in 2019, found that for the commercial sector, the meters were leaking about half a percent of all the gas that passes through them—a rate 6 times higher than the EPA estimated.


Also, existing greenhouse gas inventories usually do not include “behind-the-meter” leakage—that is, gas leakage within buildings, from pipelines running into buildings and from appliances such as furnaces and water heaters. Studies commissioned by the California Energy Commission showed that residential buildings are leaking around half a percent of the gas consumed, and commercial buildings about a quarter of a percent. As a result of this research, in 2019 California started including residential behind-the-meter leakage in their official greenhouse gas inventory.