The energy surcharge is tied to the cost of natural gas in $/Decatherm. These costs are tracked on a regional basis. The data base can be found at: https://www.eia.gov/dnav/ng/hist/rngwhhdm.htm

The monthly settlement price effective for each month and the range listed below will be used to determine the energy surcharge effective for orders shipped during the month. Monthly settlement prices are published at the start of each month.