The effect of efficiency standards on water use and water-heating energy use in the U.S.: A detailed end-use treatment

Abstract

SYNOPSISThis paper analyzes US residential water use and water heater energy use. It also investigates water and energy savings associated with existing equipment efficiency standards.Keywords: Residential codes and standards, Water heating, Water conservation, Forecasting, Program design ABSTRACTWater heating is an important end-use, accounting for roughly 16% of total primary energy consumption in the US residential sector. Recently enacted efficiency standards on water heaters and hot water-using equipment (e.g., dishwashers, clothes washers, showerheads, and faucets) will substantially affect the energy use of water heaters in the future. Assessment of current and future utility programs and government policies requires that regulators, resource planners, and forecasters understand the effects of these regulations.In order to quantify these impacts, this paper presents a detailed end-use breakdown of household hot and cold water use developed for the US Department of Energy. This breakdown is based on both previous studies and new data and analysis. It is implemented in a spreadsheet forecasting framework, which allows significant flexibility in specifying end-use demands and linkages between water heaters and hot water-using appliances.We disaggregate total hot and cold water use (gallons per day) into their component parts: showers, baths, faucets (flow dominated and volume dominated), toilets, landscaping/other, dishwashers, and clotheswashers. We then use the end-use breakdown and data on equipment characteristics to assess the impacts of current efficiency standards on hot water use and water heater energy consumption.

Baseline data for the residential sector and development of a residential forecasting database

“…Assuming a 77 F rise between the incoming cold water temperature and the hot water setpoint temperature, 45.3 gallons/dayhousehold gives UECs that are similar to the estimated UECs shown above. A more recent study shows total hot water use for average early 1990s dwellings of 59.5 gallons/day (Koomey et al 1994b). …”

Evaluation of advanced technologies for residential appliances and residential and commercial lighting

“…The 1994 NAECA minimum efficiency standards for dishwashers and clothes washers and the 1994 EPAct standards for showerheads and faucet aerators imply that hot water usage would drop to 48.1 gallons per day (Koomey, 1994). This drop would give an energy savings of about 15% to 20% for water heating as these standards are incorporated into the housing stock.…”

Energy and carbon impact from residential laundry in the United States

“…Kempton (1988) identifies hot water consumption to be behavior driven and therefore foresees large potential for energy savings. Koomey et al (1995) notes that the use behavior w.r.t. water heaters varies based on water-inlet temperatures, water-using equipment, hot water temperature-set points, water-use temperatures, water distribution system, water heater insulation, ownership of other associated appliances and their characteristics (Lutz 2005;Sabaliunas et al 2006).…”