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Comparing Gas Tankless Water Heaters

With several brands and models to choose from, how do you compare gas operated tankless water heaters?


  • Many leading brands, such as Paloma/WaiWela, are manufactured in Japan where tankless technology has been refined and produced for decades. We recommend choosing a unit that is:
    • ENERGY STAR qualified
    • Energy factor of at least 0.82
    • Warranty of at least 12 years heat exchanger/5 years parts/1 year labor
    • Third party certifications like CSA and UL


Flow Rate & BTU Requirement Considerations

  • What are your gallons per minute (GPM) versus temperature rise requirements?
    • The more BTUs you have, the greater the water flow will be at any specific temperature rise. Try comparing units at a 70 degree F increase.
  • Consider the minimum BTU for applications using preheated water (solar preheat system). The lower the minimum BTU, the more immediately the water heater will react to preheated water and produce a small change in temperature (110F + 10F = 120F).


  • Ideally, a tankless water heater should be installed on an outside wall and be vented through the same wall to keep vent runs as short as possible. Most gas tankless water heaters require a special category III stainless steel vent pipe. So it's a good idea to plan your system with these two requirements in mind.

More Venting Products: http://www.tanklesswaterheaters.com/venting.html

Other Considerations

  • Safety engineering
  • Multi-unit linking
  • Is a remote control and power cord included?
  • High-altitude capabilities
  • Freeze protection
  • Low NOx burner

For more information, visit Gas Tankless Water Heaters.

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