Disaggregating Hot Water Use and Predicting Hot Water Waste in Five Test Homes

H. Henderson, J. Wade

Research output: NRELSubcontract Report


While it is important to make the equipment (or 'plant') in a residential hot water system more efficient, the hot water distribution system also affects overall system performance and energy use. Energy wasted in heating water that is not used is estimated to be on the order of 10 to 30 percent of total domestic hot water (DHW) energy use. This field monitoring project installed temperaturesensors on the distribution piping (on trunks and near fixtures) and programmed a data logger to collect data at 5 second intervals whenever there was a hot water draw. This data was used to assign hot water draws to specific end uses in the home as well as to determine the portion of each hot water that was deemed useful (i.e., above a temperature threshold at the fixture). Five houses nearSyracuse NY were monitored. Overall, the procedures to assign water draws to each end use were able to successfully assign about 50% of the water draws, but these assigned draws accounted for about 95% of the total hot water use in each home. The amount of hot water deemed as useful ranged from low of 75% at one house to a high of 91% in another. At three of the houses, new water heaters anddistribution improvements were implemented during the monitoring period and the impact of these improvements on hot water use and delivery efficiency were evaluated.
Original languageAmerican English
Number of pages103
StatePublished - 2014

Bibliographical note

Work performed by ARIES Collaborative, New York, New York

NREL Publication Number

  • NREL/SR-5500-61441

Other Report Number

  • DOE/GO-102014-4397


  • Building America
  • DHW
  • disaggregation
  • distribution systems
  • domestic hot water (DHW)
  • energy
  • hot water waste
  • plumbing
  • residential
  • residential buildings
  • tankless water heaters


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