Energy efficiency. An LPG water heater conserves enough energy and increases energy efficiency sufficiently to reduce a family’s energy cost by approximately $75 to $300 a year compared to the cost of operating an electric water heater. Typical energy savings range from $100 to $170 a year, or $1,100 to $1,870 over the expected 11-year useful life of a water heater. Low emissions of regulated pollutants. Propane water heaters offer substantial air-quality benefits by reducing emissions of oxides of nitrogen (NOx), carbon monoxide (CO), sulfur dioxide and carbon dioxide, the main “greenhouse” gas. Compared to a typical electric water heater with a 0.93 energy efficiency factor, a propane water heater with a 0.58 energy efficiency factor reduces NOx emissions by approximately 90 percent, CO emissions by approximately 70 percent, sulfur dioxide by 99 percent and carbon dioxide by approximately 60 percent. These air pollution reduction estimates represent the difference between emissions from power plants utilizing a typical fuel mix and emissions expected from the combustion of propane in a properly adjusted water heater in good condition, as listed in U.S. Environmental Protection Agency publications on air pollution. Low greenhouse-gas emissions. Used for space heating and water heating, propane’s total fuel-cycle emissions of urban air pollutants and greenhouse gases are second-lowest after natural gas, according to DeLucchi (1999). Electricity has total fuel-cycle emissions two to four times higher than those for natural gas or LPG, according to this analysis.