Piedmont Natural Gas Co. recently filed for a reduction in its customer billing rates for customers in North Carolina and South Carolina. If approved, residential billing rates in South Carolina could decline up to 8 percent.

The filings with the Public Service Commission of South Carolina and the North Carolina Utilities Commission seek to lower the wholesale cost of gas benchmark contained within the customer billing rates in each state and follow recent declines in the wholesale cost of natural gas.

Earlier this month, the Charlotte-based company also filed a request with the Tennessee Regulatory Authority to reduce customer billing rates in Tennessee.

The proposed reductions, if approved by the respective state regulatory bodies, would each go into effect on Jan. 1.

The benchmark reflects the wholesale cost of natural gas supplies purchased by the company on behalf of its customers, which can fluctuate up or down. The wholesale cost of gas represents the single largest portion of a residential or commercial customer's monthly natural gas bill, typically 65 to 70 percent of the total bill.

As a regulated natural gas distribution company, Piedmont Natural Gas is required to "true-up" or pass through the wholesale cost of gas to its customers on a dollar-fordollar basis, without adding on any additional profit margin.