The Natural Resources Defense Council, however, has compiled emissions by utility, using the E.P.A. figures.

The report also shows that Texas has by far the highest total emissions from power plants and refineries, with 294 million metric tons of carbon dioxide equivalent spewed into the atmosphere. The next highest total comes from Pennsylvania, with 129 million metric tons.

Although sleekly presented, the E.P.A.’s registry has its limitations. It is neatly organized by state and emissions source, but that does not reflect the nature of the electric system, which is responsible for the bulk of the emissions in the inventory but is not divided by state lines. The ranking makes the District of Columbia look like a fairly small emitter and Pennsylvania like a large one. But some of the coal burned in Pennsylvania flows through the regional power grid to feed Washington and other areas.

And the emissions inventory does not capture information about the efficiency of the source. New York University, for example, may rank as a big emitter in New York, but a year ago it opened a co-generation facility that makes electricity and uses the waste heat to heat and cool buildings, thus doing far more work per pound of carbon dioxide emitted than most other sources.

Still, David Doniger, the policy director for climate and clean air at the Natural Resources Defense Council, described the new database as a “very powerful small-d democratic tool.”

“It means that every high school student or local reporter can see who the biggest carbon polluters are in his or her own backyard,” he said. “Carbon pollution and climate change are very abstract when you’re dealing with national or international data. This brings it home.”