Break-even cost for residential solar water heating in the United States: key drivers and sensitivities

Original publisher: Golden, CO: National Renewable Energy Laboratory, [2011] OCLC Number: (OCoLC)704301732 Subject: Solar water heaters -- Cost effectiveness. Excerpt: ... Figure 3. Variation in annual energy savings ( kWh / year ) for the base case SWH system with an electric auxiliary water heater As shown in Figure 3, New Mexico and Colorado have the highest energy savings, exceeding 2,400 kWh per year. Except for southwestern Arizona and northern Montana, all states in the Mountain region save over 2,000 kWh annually, as do many in the Midwest. States in the Middle Atlantic and Pacific Northwest generally have lower energy savings, dropping below 1,800 kWh annually. The amount of energy saved is primarily driven by climate factors such as solar resource, cloud cover, precipitation, and inlet water temperature. The higher the inlet water temperature ( as in Arizona ), the less energy required for water heating, and the lower the quantity of energy saved. Areas with high amounts of annual precipitation and cloud cover ( such as Oregon, Washington, and Ohio ) have less solar energy available for water heating. States with year-round good solar resource and cooler inlet water temperatures ( such as Colorado ) will have high energy savings. The solar fraction is a performance metric that indicates how much of the energy demand is supplied by the SWH system. It is typically expressed in terms of percent of total load met and varies between 0 % ( no SWH system ) and 100 % ( all energy supplied by the SWH system ). On winter days or days with inclement weather, the SWH system may meet none of the daily hot water demands, whereas on sunny, summer days, the system may save more energy than is required to satisfy 100 % of the hot water needs. This parameter will vary geographically and with time based on hot water usage and solar 7