Residential propane prices in Nevada County are at a three-year low, but with meteorologists predicting a colder winter than a year ago, energy officials expect use will outpace American’s 2011 consumption. “The prices haven’t been this low since the last election four years ago,” said Kathy Marcione, an office manager at Ace Propane in Grass Valley. Since most propane suppliers choose not to publicly post their propane prices, and most government propane price surveys are only available between October and March of each year, propane consumers have limited options to compare their suppliers propane prices. Ace Propane, which posts its …