Model # ECO 18

Internet #203316216

Store SKU #1000047991

EcoSmart 18 kW Self-Modulating 3.5 GPM Electric Tankless Water Heater


18 kW Self-Modulating 3.5 GPM Electric Tankless Water Heater

  • Perfect for apartments with up to 3 people
  • Requires 2 x 40 Amp Double Pole Breakers
  • Same-day installation in most areas. Call 1-855-400-2552 by noon.
$42500 /each
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Product Overview

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EcoSmart Electric Tankless Water Heaters, also called Instantaneous On Demand Water Heaters, provide endless hot water on demand and only as needed. Self-modulating flow sensor technology regulates the amount of energy required to heat the water needed. This Smart Technology electric tankless water heater is configured for climates where incoming water temperature is 62°F and above. The ECO 18 is capable of heating over 2.5 GPM, which is the equivalent of one shower head (with a 1.5 GPM flow) and one sink with a low inlet water temperature of 62°F. Two showers can be run simultaneously when incoming water temperature is above 70°F in warmer climates such as South Texas, South Florida, New Mexico, Arizona and South California.

  • Lifetime warranty
  • Patented self-modulating technology and design
  • Never run out of hot water with an EcoSmart tankless water heater
  • Digital temperature control allows you to set your temperature in increments of 1 degree
  • All EcoSmart electric tankless water heaters come with an automatically resettable thermostat as opposed to a manually resettable thermostat; the integration of all components and quick connections are designed to promote simplicity for the installer and the user
  • Prior to purchase and installation please verify this model is the rights size for your hot water needs and electrical requirements
  • Refer to the info and guides for help with: location specifications map, installation, and troubleshooting
  • Easy to maintain
  • A reliable hot water solution from EcoSmart
  • Selection Guide
  • Other models available
  • Click here to check out our buying guide on water heaters
  • Click here for more information on Electronic Recycling Programs

Info & Guides

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Name 11 kW Self-Modulating Electric Tankless Water Heater 18 kW Self-Modulating 3.5 GPM Electric Tankless Water Heater Performance 18 kW Self-Modulating 3.5 GPM Electric Tankless Water Heater 27 kW Self-Modulating 5.3 GPM Electric Tankless Water Heater
Brand EcoSmart EcoSmart Rheem EcoSmart
Ratings (76) (147) (4) (180)
Wattage (watts) 11000 18000 18000 27000
Indoor/Outdoor Indoor Indoor Indoor Indoor
Water Heater Features Wall Mountable Wall Mountable Wall Mountable Wall Mountable
Flow Rate @ 45 F Rise (gallons/min) 1.97 2.73 2.73 4.10
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Product Depth (in.)
Product Height (in.)
Product Width (in.)
Water Connection Size (in.)
3/4 In. NPT


Amperage (amps)
Application Type
Electric Product Type
Energy Factor
Finish Family
Flow Rate @ 35 F Rise (gallons/min)
3.51 gal (US)/min
Flow Rate @ 45 F Rise (gallons/min)
Flow Rate @ 55 F Rise (gallons/min)
Flow Rate @ 65 F Rise (gallons/min)
Fuel Type
Heat Exchanger Warranty
Maximum Temperature (F)
Minimum Activation Rate (gpm)
Minimum Temperature (F)
Product Weight (lb.)
Required Volt Connection
Uniform Energy Factor
Water Connection Location
Water Heater Features
Wall Mountable
Wattage (watts)

Warranty / Certifications

Certifications and Listings
1-UL Listed,CSA Listed,ETL Listed
Labor Warranty
No Warranty
Part Warranty

More Products With These Features


Customer Questions & Answers

what causes the heating element to turn on?

Is it always adding a little heat to the manifold, and a temperature drop switches on the power. Or is it pressure or flow sensing?
Asked by: MikefromFL
Watch the video!!! :) That is what the video is there for... it will tell you exactly how the heating element works. I am purchasing one tomorrow, I will report the pro's and cons after it is installed and tested. Have a Great Day!!
Answered by: Bailey
Date published: 2017-04-26

Is this for a whole apartment or a single point?

Asked by: rh27
I have a 4 bedroom house and at most we only have 1 shower and 1 sink running at the same time but we have to turn it down as the water comes out too hot at times.
Answered by: Anonymous
Date published: 2017-06-25

Can these units be plugged In a 240 electrical socket

Asked by: GlenRay
Highly unlikely. It actually requires 2 separate 40 amp 240volt services. It draws 75 amps of 240volts at peak use.
Answered by: Hogie
Date published: 2017-04-29

can i use CPVC pipe

can i use CPVC pipe
Asked by: gale
Answered by: buck0522
Date published: 2017-06-25
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Customer Reviews

18 kW Self-Modulating 3.5 GPM Electric Tankless Water Heater is rated 4.2 out of 5 by 146.
Rated 5 out of 5 by from I purchased an ECOSMART 18 a couple weeks ago. As I installed it myself (not recommended), I'll d... I purchased an ECOSMART 18 a couple weeks ago. As I installed it myself (not recommended), I'll detail the challenges I ran into while installing. Please remember it is recommended to have a professional install this. First and foremost, the 18 model requires two separate 40 amp breakers with two separate 8 gauge romex (black, red, ground). You need to check that your breaker box can accommodate this. My old water heater ran on a single 60 amp breaker with one run of wire. I was able to reuse the old wire as it was the proper gauge, but had to change the breaker to 40 amp, add a second 40 amp breaker and run a second run of 8 gauge romex through the attic. Plumbing: whatever you do, DO NOT USE PVC or other plastic products to route your water. While I used galvanized steel as a temporary measure here (see picture), I'll be replacing that with all brass parts. DO use high quality hoses to connect heater to inlet and outlet. FLUSH THE INLET before connecting to the heater. This is important! Before giving the unit power, flush cold water through the heater by turning on all sources of hot water points to purge the system of air. In the box is a good set of directions you should definitely read. In fact, read it many times if you choose to do this yourself. If you do not understand any of the directions, get a professional to help you. Ok, how does it work? I bought the 18 model as I'm usually the only person in the house. I have one bathroom, and the only other hot water source is in the kitchen. I have the unit set at 140 deg F, because that's just me. 120 deg F is better for those who don't want to accidentally get scalded. Shower: it takes just a little longer to get the hot water going. Maybe 20 seconds, but man once it gets going, you can take as long a shower as you want. Doesn't blink an eye. My kitchen sink takes about 30 seconds to heat up, but that's because it's about 30 feet from the heater. I ran a test to see how it would handle running a shower and kitchen faucet at same time. At first it struggled to send hot water to both at same time. To fix this, I installed a water limiter/ aerator at the sink. This solved the problem. I am very pleased with my new ECOSMART water heater. Endless hot water AND I will save $$ on my power bill, because I no longer have to continually keep a 50 gallon tank hot. The initial cost is more than a traditional heater, but this little guy will pay for itself in under a year. Remember, if you do this yourself, you will save money, but don't take chances if you're not sure. I do recommend hiring a professional and having it inspected. Check your local ordinances if you're unsure. Also remember to get the right unit for your circumstances. i.e. number of people in house, sources of hot water in home, and available breaker space in your breaker box. Good luck! :)
Date published: 2017-04-11
Rated 5 out of 5 by from This is a great product. Our power bill has gone down $20 dollars a month this item is literally... This is a great product. Our power bill has gone down $20 dollars a month this item is literally paying for itself. I have a baby and I am able to set the temperature so when the "hot" water comes out it is a safe and I don't have to worry about scalding. It is so easy to change the temperature using the dial we no longer mix cold and hot water to get the perfect shower. We now just turn the hot water setting at our preference and then turn the hot water all the way on.
Date published: 2017-05-30
Rated 5 out of 5 by from VERY IMPRESSED. I live in Cincinnati, it is currently spring, so the incoming water temperature m... VERY IMPRESSED. I live in Cincinnati, it is currently spring, so the incoming water temperature may be higher than winter, but reading the charts and using a thermometer, it was between 52-57 degrees. I was very skeptical, and really wanted the Eco 27, however our current house is only 150amp service. So I was kind of left without a choice of the 18 or smaller. Grant it, I have only had this unit for a few days, but, I set the temp at 120 because my daughter said she had to have "hot" showers, plus she is the one that would normally take a long enough shower to empty an 80 gallon tank style. Either way, I got in the shower after her, and 120 was too hot for me. I dropped it down to 115 degrees. and am still VERY IMPRESSED, still had hot water that just kept coming. The little Eco 18 performs top notch...two days in.
Date published: 2017-04-14
Rated 5 out of 5 by from I really like this tankless water heater. It was easy... I really like this tankless water heater. It was easy to install and I had it plumbed an wired in about 2 hrs. So far it has provided great hot water for a house with 2 showers. I like the turn dial temperature adjust as it makes it very easy to change the max temperature.
Date published: 2017-04-07
Rated 2 out of 5 by from I went with this unit purely for the requirements of... I went with this unit purely for the requirements of the electrical box, I was maxed out with two forty amp fuses. At 3.5 gal per minute combine with water temp in the mountains, it is less than ideal. It does work and u won't run out of hot water, but u can't exceed about 20% of the shower flow
Date published: 2017-03-28
Rated 5 out of 5 by from Love it I purchased a small restored 1930's Carriage home in Florida that has 1 bath and of course a kitchen. This unit was brand new and already installed do to not having any room for a traditional hot water heater. the water would get really hot for the sinks up to 140° but the shower would only get lukewarm.. I thought it was an issue with the hot water heater but it turned out to be the Delta shower had a temperature control inside the knob that needed to be adjusted. once I adjusted the shower control to allow the knob to turn all the way, now my shower gets very hot and I can run both sinks and the shower at the same time and they all stay hot. My water and electric bill stays low.
Date published: 2016-12-03
Rated 4 out of 5 by from bought this one as my traditional water heater was slowly dying, replaced it on Oct 10 2016 First... bought this one as my traditional water heater was slowly dying, replaced it on Oct 10 2016 First day everything worked with out a hitch, day two had to reset the unit by tripping the breakers, day five unit was not working, called the company, left message they called me back the next day, they overnighted a new flow sensor, I installed the new one with out any issue and have not had am issue since. Customer service was fast, and very polite. I will see with next months FPL bill if its going to pay for itself.
Date published: 2016-10-24
Rated 1 out of 5 by from Only worked for 2 months and then customer service won't respond We purchased this from Home Depot online and then had it professionally installed by a licensed plumber as required. It worked OK for about 2 months. Although the temperature would fluctuate quite a bit during a shower. Then one it stopped getting hot. I turned the temperature all of the way up and it will only get lukewarm. Tried to contact their support and have received no response. Sent an email from their web site, then called the customer service number. After spending a long time on hold I opted for the option to save a message and have a customer rep call me back. It has been a week and nobody has called me back. Customer service has been very disappointing.
Date published: 2016-03-28
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