Whole Home Tankless Gas Water Heaters


By heating water only when it's needed, ENERGY STAR certified gas tankless water heaters cut water heating expenses, while also providing continuous hot water delivery. Gas tankless models are a great choice for new construction and major remodeling, but are also becoming popular as a replacement for gas storage water heaters. Read our Gas Water Heater Factsheet (PDF, 83 KB) to learn more.

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What else should I look for when buying a whole-home gas tankless water heater? 

ENERGY STAR qualified gas tankless water heaters are currently available from contractors and retailers. If you are building a new home, or in the market to replace your existing gas water heater, consider these purchasing tips:

  1. Plan ahead if you can. To make your life easier, plan ahead for your next water heater replacement and you will have time to research and select the best technology for your situation before it's an emergency. Your installer may need time to order the proper model, and it may take longer to install than a standard water heater.
  2. Check product availability. Find out what certified models are available on the market by viewing the ENERGY STAR Product List. You will then need to visit manufacturer Web sites, call local installers, or visit your local retailer to determine who carries these units in your area, or call your plumber or contractor to see what products are available.
  3. Estimate the capacity you'll need. While the capacity of gas storage water heaters is based on the number of gallons that will fit in the tank, tankless models are rated by how many gallons of hot water they produce per minute (GPM). The more likely you are to have the shower, dishwasher, and clothes washer going at once, the larger the GPM you will need.
  4. You will need to consult with an experienced plumber to estimate the hot water demands in your home, but here are some average figures:
    • Shower and Bathtub - 2.5 GPM
    • Clothes Washer - 3.3 GPM
    • Kitchen and Bathroom Sink - 2.2 GPM
    • Dishwasher - 1.3 GPM
  5. Schedule an in home estimate with an installer. You may want to check a manufacturer or retailer's Web site to get a general idea of cost, but you will eventually need an installer to come to your home and give you a customized price. The installer should confirm the optimal GPM size for you home, determine whether your existing natural gas line is sufficient, whether electricity is available near the water heater (for forced ventilation models), and identify how the combustion gases will be vented. When requesting a quote, remember to:
    • Request cost estimates in writing.
    • Ask for references.
    • Check the company with your local Better Business Bureau.
    • See if the company will obtain a local permit if necessary and understands local residential building codes.
  6. Search for rebates. You may be able to reduce your costs by taking advantage of rebates. Be sure to review the eligibility rules before you make your purchase.
    • Use the Special Deals Finder to determine whether there are rebates available for ENERGY STAR certified water heaters in your zip code.
  7. Consider other measures that may also save energy. If you are in the midst of new construction or home remolding project, you may have come across other proposed approaches to water heating. Under the right circumstances, these technologies can save significant amounts of energy.

Be sure to look for the ENERGY STAR when shopping for a whole home tankless gas water heater

Current Specification Effective Date: April 16, 2015

The specification covers high-efficiency gas storage, whole-home gas tankless, solar, and high efficiency electric storage water heaters. Products must meet minimum requirements for energy efficiency, hot water delivery, warranty period, and safety.

Water Heater Key Product Criteria: ENERGY STAR

Learn How a Product Earns the Label

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