If you heat your home with natural gas, Ameren Illinois says prices will stay about the same as they were last winter. Ameren's Scott Glaeser says an increased supply and a sluggish economy mean customers won't see much of an an increase in prices. Ameren customers paid an average of 61-cents a therm during the last season. This year, that price is expected to be about 62-cents a therm. Glaeser says Ameren has secured an adequate supply to meet customer needs this winter and most of the gas is price protected.