Natural gas utilities in Indiana and throughout the nation purchase gas on the competitive national wholesale market. This includes buying some of their gas - but not all - on the spot market. Utilities use a number of tools - including spot market purchases, futures contracts and storage - in purchasing gas and planning for the winter heating season each year. All of these factors affect retail natural gas prices.
The OUCC's natural gas prices (http://www.in.gov/oucc/2387.htm) and gas cost adjustments (http://www.in.gov/oucc/2388.htm) fact sheets offer additional information.