The amount of carbon dioxide emitted from energy use in the United States increased last year because of the brutal winter, the Energy Department said.

The department's Energy Information Administration said energy-related CO2 emissions increased 2.5 percent from 2012 levels.

"The 2013 increase was largely the result of colder weather leading to an increase in energy intensity," EIA said in a Tuesday report.

PJM Interconnection, a company operating the electric grid for more than a dozen Midwest and mid-Atlantic states, twice broke records for seasonal use early this year during the brutal cold snap brought on by a weather phenomenon known as a polar vortex.

The company had called for conservation measures as most states east of the Mississippi River endured temperatures well below the freezing mark for several days.

"Weather played an important role in the year-to-year increase in CO2 emissions," EIA said. "Residential emissions were up the most of any sector."

Despite the increase, EIA said emissions are still 10 percent below their 2005 levels.