Lawrence Berkeley National Laboratory

Hot water use in households, for showers and baths as well as for washing clothes and dishes, is a major driver of household energy consumption. Other household uses of water (such as irrigating landscaping) require additional energy in other sectors to transport and treat the water before use, and to treat wastewater. In California, 19 percent of total electricity for all sectors combined and 32 percent of natural gas consumption is related to water. There is a critical interdependence between energy and water systems: thermal power plants require cooling water, and water pumping and treatment require energy. Energy efficiency can be increased by a number of means, including more-efficient appliances (e.g., clothes washers or dishwashers that use less total water and less heated water), water-conserving plumbing fixtures and fittings (e.g., showerheads, faucets, toilets) and changes in consumer behavior (e.g., lower temperature set points for storage water heaters, shorter showers). Water- and energy-conserving activities can help offset the stress imposed on limited water (and energy) supplies from increasing population in some areas, particularly in drought years, or increased consumption (e.g., some new shower systems) as a result of increased wealth. This paper explores the connections between household water use and energy, and suggests options for increased efficiencies in both individual technologies and systems. Studies indicate that urban water use can be reduced cost-effectively by up to 30 percent with commercially available products. The energy savings associated with water savings may represent a large additional and largely untapped cost-effective opportunity.