EcoSmart ECO 18 Electric Tankless Water Heater

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Editor’s Conclusion
The ecoSmart ECO 18 is an 18-kilowatt tankless electric water heater ideal for providing hot water for apartments, condominiums, townhomes, and other whole-home applications - without a storage tank. When you need hot water, the unit heats up what you need on demand. Unlike a unit with a tank where you heat all the water in the tank for whenever you might need it, tankless units like the ECO 18 starts heating the water after you have turned on the “hot water” so you only pay for what is delivered, not for keeping 40 or 50 gallons of water warm “just in case” you do. Tankless systems are big energy savers!

A tankless water heater can help you save on your energy bill; buying a specific model that meets or exceed your likely need will assure you will have all the hot water you need when you need it. The ecoSmart ECO 18 is part of a line of models each distinguished by their kW that corresponds to the temperature of groundwater in your area.

The EcoSmart ECO18 is a mid-range product recommended for a large apartment or townhome that houses up to 3 people, while the ecoSmart ECO 36 delivers twice the flow for larger homes and commercial locations. Customers in cooler climates might want to move up to one of the larger kW products. This unit runs $368 on Amazon vs. $599 for the ECO 36, but given that the greatest expense in getting these tankless products in the home is in installation, spending a couple hundred more on the product might be well worth it.

EcoSmart was part of the Eemax family of tankless electric water heater brands, but Rheem acquired Eemax in 2015. The deal merged the largest producer of gas-fired tankless water heaters, as well as energy-efficient tank, solar, and hybrid water heating systems with a leading manufacturer of electric tankless water heating solutions for residential, commercial, and industrial applications in the U.S. to create a powerhouse brand.
Editor's Pros & Cons

Compact unit produces endless hot water

Only consumes energy when hot water is required

No Stand-by or Cycling loss

Temperature adjustable in 1° increments

Limited lifetime warranty if professionally installed


Elements may corrode quickly

Professional installation required

Unit may corrode if water is not mineral free

Warranty must be registered within 30 days of purchase

Key Features

The ecoSmart ECO 18 Electric Tankless Water Heater has stainless and copper components, along with a plastic housing. The unit weighs just 11.25 lbs. and measures 17" x 14" x 3.75", so it compactly fits on a wall right near the point of use. The unit not only saves on fuel cost and usage because it has no stored water to heat up but because the water may have to travel a shorter distance after heating.
Though the action takes place in the heat exchanger tubes, the user can control the temperature of the hot water with a digital thermostat on the outside.

Notable Features

As compared to water heaters with storage tanks, the ecoSmart ECO 18 electric tankless hot water heaters is energy efficient while still giving you the option to set the appropriate water temperature for bathing, dishwashing, or clothes washing.

With a tank, a portion of the large volume of water stored in the tank heats up to the desired temperature when needed before the thermostat kicks off. the unit stops consuming energy, the water cool down – a phenomenon known as Stand-by Loss. To get the water back to the set temperature, the unit clicks on and starts consuming energy again. When some water is used, cool groundwater runs into the tank and lowers the temperature of the water there. This so-called Cycling Loss makes the element kick into action and consumes energy. The ECO 18, in contrast, eliminates Stand-by and Cycling losses by only using energy when someone turns on the hot water faucet or rotates the control on the washer or dishwasher – which leads to savings of 20%. Heating just the water you need results in total savings of 50-60%.

Every time hot water is required, the whole tank heats up. When the supply is depleted, more cool water comes into the tank, which lowers the temperature of the rest of the water in the tank, and when someone turns on the hot water faucet, the whole process of heating up the water in the tank repeats.


Deciding on the right size tankless unit depend on three factors:

Watts, the energy required to heat the water on demand to reach the desired temperature
Temperatures rise, the groundwater temperature vs. the required temperatures
Flow rate (gallons per minute – GOM=

The ECO 18 requires 18 kW of power to warm up water that flows into the home and provides between 1.8 and 4.3 gallons per minute depending on the inlet water temperature in your region.

Because the temperature of incoming water in Hawaii (75°) is much warmer than that in Alaska (35°-42°) the more water that can be available for multiple simultaneous uses in the home. Someone with a low inlet temperature might be able to have just one or maybe two showers, hand washes, dishwasher, or washing machine uses in progress at the same time, while a homeowner in a warmer inlet area might be able to have as many as five simultaneous uses.


Tankless water heaters have a life expectancy of over 20 years – nearly double that of a tank system. At 99.8% efficient compared to 65% for tanks, they save homeowners money every year. Proper maintenance will guarantee their long life.

When water is “hard” and full of mineral deposits, the heat exchanges are subject to scale build-up. Before installing a tankless system, ecoSmart recommends installing a water treatment or water softener system to protect the new tankless equipment.

Each year, the system should be inspected for leaks, cracks, weakness, potential failures, or any signs of damage. When area water is hard, inspecting the system more frequently will alert the homeowner to problems that could shorten the life of the system and invalidate the warranty.

Doing any maintenance on the system requires turning it off at the breaker box to prevent injury or death. When repairs are complete, purging the air from the lines before powering up the unit is crucial before restarting the systems to avoid damaging the heating element and voiding the warranty.

Eco 18 heater

Comparison to Other Products

The ecoSmart ECO 18 has over 3,400 global ratings on Amazon with 86% of them 4 or 5 stars. The remaining 14% with lower ratings concentrate on warranty issues or corrosion of parts. Professional installation is very costly but the warranty if invalid without it. Installing the unit requires not just the services of a plumber but of an electrician as well.

Our Verdict

The brand of tankless electric water heater brand often makes it to the top of “Best Tankless Electric Water Heater “ lists. The Chicago Tribune rated it a customer favorite that offers the best band for the buck.

If you are willing to opt for professional installation, the ecoSmart ECO 18 might be a good choice for your small home.