This analysis estimates the energy savings potential and associated costs of individual design options or combinations of design options. Design options added to baseline residential water heaters reduce water heater energy consumption and can save United States consumers billions of dollars per year. To determine the energy-saving viability of particular design option combinations, both the potential energy savings and the estimated costs were calculated. Energy use for design options for each of the three classes of water heaters were modeled either with computer simulation programs or a simplified calculation method. Water heater manufacturers, distributors, and industry experts provided the cost data. The analysis then developed a price relationship to show the manufacturer and consumer cost to achieve increased efficiency. The results show that energy efficiency measurements can be increased by 4% for electric water heaters, 9% for gas-fired water heaters, and 2% for oil-fired water heaters. These results indicate that acceptable paybacks can be achieved for electric and gas-fired water heaters. This information serves as the basis for proposed changes in energy efficiency of U.S. residential storage-type water heaters.Units: Dual