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Last month, we gave you the pros and cons of buying a tankless water heater (click here to see the blog).  This month we want to give you some advice on buying a tankless water heater, if that is how you decide to go.  As a reminder, here are the benefits:

  • They can be more energy-efficient than standard units
  • They take up less space
  • They outlast standard units if properly maintained

And the drawbacks:

  • They are limited by the flow rate of water through the unit
  • It takes them longer to produce hot water
  • A separate storage tank needs to be installed if you want to use it with a hot water return line
  • The unit must be delimed every three years
  • Replacement parts may be difficult to obtain

So here are some things to consider when buying a tankless water heater:

Heat Output and Flow

A tankless water heater’s output is a function of groundwater temperature. The higher the temperature, the greater the volume generated as measured by gallons per minute (GPMs).  All products have ratings for the amount of heat generated (measured in BTUs or kilowatts) and GPMs.  Make sure whoever you are purchasing the unit from calculates the GPMs you require.  Then buy the unit that produces at least that much.  Undersizing is a common mistake.  Err on the side of oversizing.  You don’t want to be surprised by a sudden burst of cold water.

Temperature Adjustment

You can control the temperature with everything from a simple knob to a panel of complex, automated flow controls.  Select whatever you are most comfortable with.

Safety Features

There are two important safety features.  First, make sure your unit has an oxygen-depletion sensor that shuts off the water heater if carbon monoxide is detected.  Also make sure the unit has a high limit switch  that will shut off the unit if it gets too hot.


Get as long a warranty as you can, and check out any exclusions.  Some installers will offer extended warranties.

Don’t DIY

It is important that your water heater be professionally installed.  First of all, a professional is trained to do this, and should also be licensed and insured.  In fact, some companies will extend your warranty if you have it professionally installed.

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