Preliminary Modeling, Testing, and Analysis of a Gas Tankless Water Heater: Preprint

Research output: Contribution to conferencePaper


Today's gas tankless water heaters offer significant energy savings over conventional gas storage tank water heaters, but savings depends on the draw pattern. A one-node model incorporating heat exchanger mass is used to address this and other issues. Key model parameters are determined from least-squares regression on short-term data, including burner efficiency, thermal capacitance, and thermalloss coefficient. The calibrated model agrees with data to~5% on Qgas, with temperature RMS deviation of~4..deg..C. Efficiency with a standard realistic draw is 71%, compared to 81% predicted from standard energy-factors. Adding a small tank controlled by the tankless heater solves issues of oscillations with solar pre-heat, low-flow and hot-water-delay issues. Future work includes modelrefinements and developing optimal data protocols for model parameter extraction.
Original languageAmerican English
Number of pages11
StatePublished - 2008
EventSOLAR 2008 - San Diego, California
Duration: 3 May 200810 May 2008


ConferenceSOLAR 2008
CitySan Diego, California

NREL Publication Number

  • NREL/CP-550-42917


  • least squares regression
  • tankless water heaters


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