At the simple inputs level of the Home Energy Saver, users are asked to select the fuel of their water heater. The water heater characteristics (tank size, year purchased, etc.) are defaulted based on choice of water heater fuel. The values for recovery efficiency and rated input for the water heater are derived from manufacturers' product specifications (GAMA 1996) for typical models of each fuel type. Tank size was taken from Table 4.4 of the Energy Data Sourcebook (Wenzel 1997).