Why your electric bill drops when natural gas prices do

A fracking rig at a well site for shale based natural gas in Zelienople, Pa.
A fracking rig at a well site for shale based natural gas in Zelienople, Pa. AP

Duke Energy’s rapid turn to natural gas to fuel its power plants is contributing to slightly cheaper electricity for its Charlotte customers.

Gas supplies are outstripping demand, so prices have dropped to historic lows. Duke expects gas prices to be 32 percent cheaper over the next year than they were in 2015.

Because Carolinas utilities aren’t allowed to profit from fuel, the savings are passed to customers.

The N.C. Utilities Commission on Tuesday adjusted fuel charges that, combined with separate changes to energy-efficiency and renewable energy fees, will save residential customers of Duke Energy Carolinas $3.13 a month starting in September. Duke Carolinas serves Charlotte and western North Carolina.

Duke has filed similar requests, reducing customer bills from $3 to nearly $6 a month, in eastern North Carolina, South Carolina, Ohio and Florida.

Gas is plentiful because the drilling technique called hydraulic fracturing, or fracking, has tapped shale reserves in the Northeast and Southwest in recent years.

Fracking is controversial. It’s been linked to increasing numbers of earthquakes, contaminated water and the release of climate-warming methane gas.

But because gas is cheaper, and burns more cleanly than coal, Duke Carolinas upped its gas use 38 percent in 2015 while using 18 percent less coal. Nuclear energy continues to generate nearly half of the utility’s electricity.

Duke was before the Utilities Commission last week to seek approval of a $4.9 billion acquisition of Piedmont Natural Gas. The companies are already investors in the $5 billion Atlantic Coast Pipeline, to pipe gas from West Virginia to eastern North Carolina, and hope to invest in more such projects.

Bills for Duke Energy Carolinas customers will drop as a result of two changes approved Tuesday.

One adjusts the actual costs of fuel in 2015, which were $41 million lower than the utility had estimated. The other reduces estimated fuel costs for September through next August by $195 million.

The lower fuel costs will be reflected in bills starting Sept. 1.

Bruce Henderson: 704-358-5051, @bhender