Best tankless water heater

  • 99.8 percent efficiency
  • Point-of-use; heats water on demand
  • Small unit doesn't take up much space
  • Lifetime parts warranty
  • Performance can vary depending on water temperatures
  • No labor warranty; company may not honor parts warranty on self-installs

Bottom line

If you're looking for a tankless, energy-efficient water heater, the Ecosmart ECO 27 is a top choice. It's well regarded by experts and owners, and has a long warranty, albeit with some catches. The ECO 27's got excellent energy efficiency, too, but performance can vary greatly depending on the temperature of your water supply. The tiny box looks easy to install, but there are some considerations that might make things a bit more challenging.

Breaking it down


Ample hot water under the right conditions. For most locales, the Ecosmart ECO 27 can produce plenty of hot water on demand. Things get dicey in colder regions, however, and if your water supply is very cold (around 37 degrees Fahrenheit), don't expect to have enough hot water to do much more than take a single shower at a time. Ecosmart provides a handy reference chart that lists inlet water temperatures in different regions of the country and the amount of hot water you can expect in each one. You can tweak water output by raising or lowering the hot water temperature, and that can be done in 1 degree increments. Installation can be easy or hard, depending on your set up. On the plus side, the ECO 27 is far more compact than a typical storage tank hot water heater. On the minus side, it may require reworking plumbing as the water inlet and outlet are on the underside of the unit rather than on top, as is typical in storage tank hot water heaters. In addition, it requires 200 amp, 240 volt electrical service.


Cuts electricity costs. Other than producing hot water on demand in sufficient quantities, the biggest selling point for tankless water heaters like the ECO 27 are the energy savings. Though not Energy Star Qualified, the ECO 27 boasts a 99.8 percent efficiency rating, high enough to cut energy costs by around 50 percent.

Reliability and warranty

Great warranty, but there are catches. The Ecosmart ECO 27 is covered by a lifetime warranty, but there are some things to be aware of. One is that the warranty is for parts only, not labor. Second, Ecosmart requires that the ECO 27 be correctly installed by qualified individuals for that warranty to be honored. We've seen multiple reports of DIYers doing the job themselves and having no issues getting the warranty honored, but others have seen claims rejected over installation issues. If that's a concern, be sure to budget the cost of a licensed plumber and, possibly, an electrician into your calculations of up-front costs. The ECO 27 has been around for a number of years and has built up a reasonably large pool of user reviews. While not everyone is pleased, most owners say that the ECO 27 delivers what it promises.

Where To Buy
Ecosmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts with Patented Self Modulating Technology

 (546 reviews)
Buy new: $569.00 $432.99   29 Used from $352.46

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Ecosmart ECO 27 Review


The Ecosmart ECO 27 earns an overall rating of 4.3 stars out of 5 based on nearly 370 reviews. More than 80 percent rate it at either 4 stars or, mostly, 5 stars. Some complaints over build quality issues are noted. Others have issues with the quantity or temperature of the hot water delivered or with the warranty terms.

Review: Ecosmart ECO 27 Electric Tankless Water Heater, Contributors to, As of July 2015


Nearly 100 owners provide feedback on the Ecosmart ECO 27 at, where it earns an average rating of 4.1 stars out of 5. Complaints mirror those at, but around 84 percent say that they would recommend the ECO 27 to a friend.

Review: EcoSmart ECO 27 27 kW Self Modulating 5.3 GPM Electric Tankless Water Heater, Contributors to, As of July 2015


Here, former HVAC technician and contractor Richard Reed gives his take on tankless water heater brands, but not specific models. He names Ecosmart as the "World's Best Electric Tankless Water Heater. "These units are available in a wide range of sizes and are backed by a very good guarantee," Reed says.

Review: Tankless Water Heater Ratings, A Repairman Reviews The Brands..., Richard Reed, Not Dated

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