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Predictive Control of Hot Water Heaters

National Renewable Energy Laboratory

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PDF Document PublicationFull Report on Heat Pump Water Heaters (15,810 KB)

Technology Marketing Summary

Water heating in residential homes can account for as much as 15% of total energy use. It is the second largest end use after space heating and cooling. With a renewed interest in energy efficiency for both financial and environmental reasons, water heater companies have seen increased demand from consumers for more efficient water heaters. While various technologies have been developed, control systems can add significant savings to the best technologies.


NREL scientists have created a hot water heater control system to optimize the efficiency and comfort of homeowners. The systems were designed primarily for heat pump water heaters and gas fired water heaters, but could be modified to fit various technologies. The technology ‘learns’ users’ hot water consumption patterns from historical data and automatically modulates the thermostat set point to conserve energy while maintaining thermal comfort. Day of the week and time are recorded with data being reevaluated every 20 days. The starting time of hot water draw events is recorded and used for clustering analysis. Time intervals are generated from the clusters in which hot water draw events are more likely to occur. The set point is set at a normal level to maintain thermal comfort, and decreased to a lower level outside these time intervals to reduce tank loss and thereby improving energy efficiency of the water heater. Simulations have indicated that up to a 20% energy savings can be realized by the technology when using heat pump water heaters.

NREL is looking to license the technology or partner with a company to further develop the technology.

  • Smart water heater
  • Increased efficiency
  • Easy installation
Applications and Industries
  • Consumer appliances
  • Home energy efficiency
  • Water heater manufacturers
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Application 20150253051
Model predictive control methods are disclosed which provide, among other things, efficient strategies for controlling heat-transfer to a fluid.
National Renewable Energy Laboratory 03/09/2015
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
ROI 13-77, 13-77DevelopmentAvailable02/28/201402/28/2014

Contact NREL About This Technology

To: Erin Beaumont<>