EcoSmart Tankless Water Heaters

EcoSmart is a retail-focused electric tankless brand, and the range is more coherent than its marketing suggests. The ECO 27 and the ECO 11 are genuinely different products for genuinely different jobs, and the mistake people make is buying the first for a house that can only feed the second.

The range, with the electrical truth

Quick picks

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Ranked picks with what each one is best for, our score and a link to check the current price on Amazon.

#	Product	Best for	Price
1	EcoSmart ECO 27The biggest electric unit most homes can actually feed: 27 kW across three 40 A breakers, 6.6 GPM maximum, and a lifetime limited warranty on the unit.	Maximum electric output	Check price on Amazon No live price feed on this site, so we show none. #ad
2	EcoSmart ECO 11A single-fixture electric unit, not a whole-house one: 13.8 kW at 240 V delivering 1.3 to 3.2 GPM depending entirely on how cold your inlet water is.	One fixture, or a warm-inlet apartment	Check price on Amazon No live price feed on this site, so we show none. #ad
3	Stiebel Eltron Tempra 24 PlusThe electric tankless to buy if you are going to buy one at all: it publishes its full rise-versus-flow curve, and the Advanced Flow Control throttles flow instead of letting the temperature sag.	Whole-house electric, warm inlet	Check price on Amazon No live price feed on this site, so we show none. #ad

The picks in full

Pick 1 — Maximum electric output

EcoSmart ECO 27

The biggest electric unit most homes can actually feed: 27 kW across three 40 A breakers, 6.6 GPM maximum, and a lifetime limited warranty on the unit.

Published specifications for the EcoSmart ECO 27

Output	27 kW at 240 V, single phase
Current draw	113 A
Breakers	3 x 40 A
Wire	3 x 8 AWG
Maximum flow	6.6 GPM
Minimum activation flow	0.3 GPM
Dimensions	17 in x 17 in x 3-5/8 in
Weight	14.7 lb
Connections	3/4 in NPT
Warranty	Lifetime limited

What is good

• +Highest output of any single electric unit here, so it holds temperature at higher flow
• +Lifetime limited warranty on the unit is unusual at any price
• +3-5/8 inches deep — it genuinely disappears on a wall
• +0.3 GPM activation flow is the lowest on this page

What is not

• −113 A of draw needs three circuits and, in practice, a 200 A service
• −The published flow is a maximum, not a rise-qualified figure — you have to do the rise math yourself
• −No buffer, so a sudden flow change is felt at the shower head

Skip it if: Skip it if your panel is 100 A or 125 A. Three 40 A circuits and 113 A of draw is a service upgrade, and a service upgrade usually costs more than the entire water heater.

Check price on Amazon

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Specifications above from EcoSmart ECO 27 technical data (BIMobject). We have not tested this unit ourselves.

Pick 2 — One fixture, or a warm-inlet apartment

EcoSmart ECO 11

A single-fixture electric unit, not a whole-house one: 13.8 kW at 240 V delivering 1.3 to 3.2 GPM depending entirely on how cold your inlet water is.

Published specifications for the EcoSmart ECO 11

Output	13.8 kW at 240 V; 11 kW at 220 V
Flow	1.3 - 3.2 GPM depending on inlet temperature
Breaker	60 A double-pole
Wire	6 AWG
Current draw	54 A
Energy factor	0.998
Set point	Digital, 1°F increments

What is good

• +One 60 A circuit instead of three, which many existing panels can take
• +Honest published flow range tied to inlet temperature
• +Small and light enough for a utility closet or under a counter
• +Good match for a single shower in a warm-inlet region

What is not

• −3.2 GPM is only reachable with warm inlet water
• −Still 54 A — not a plug-in appliance
• −No modulation headroom if a second fixture opens

Skip it if: Skip it as a whole-house heater anywhere north of the Sun Belt. At a northern winter inlet temperature it lands at the bottom of its range, which is a hand-wash flow rate, not a shower.

Check price on Amazon

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Specifications above from EcoSmart ECO 6 / 8 / 11 specification sheet (PDF). We have not tested this unit ourselves.

Pick 3 — Whole-house electric, warm inlet

Stiebel Eltron Tempra 24 Plus

The electric tankless to buy if you are going to buy one at all: it publishes its full rise-versus-flow curve, and the Advanced Flow Control throttles flow instead of letting the temperature sag.

Published specifications for the Stiebel Eltron Tempra 24 Plus

Output at 240 V	24 kW
Output at 208 V	18 kW
Breakers	2 x 50 A double-pole
Wire	2 x 6 AWG copper
Current draw	100 A
Minimum electrical service	150 A
Rise at 240 V	54°F at 3.0 GPM; 73°F at 2.25 GPM; 37°F at 4.5 GPM
Rise at 208 V	41°F at 3.0 GPM; 54°F at 2.25 GPM; 27°F at 4.5 GPM
Maximum flow	8 GPM

What is good

• +Publishes rise at four flow rates on both voltages, which is the only honest way to size an electric tankless
• +Advanced Flow Control cuts flow to hold the set temperature rather than delivering lukewarm water
• +No venting, no gas line, no condensate
• +Small enough to go in the cabinet it replaced

What is not

• −100 A of draw and a 150 A minimum service rules out a lot of older houses
• −At 208 V it loses a quarter of its output, and plenty of homes are nearer 208 than 240
• −Running cost follows the electric rate, which is usually worse than gas per BTU

Skip it if: Skip it if your inlet water drops to 45°F in winter and you want two showers at once. At a 73°F rise it delivers 2.25 GPM — one shower, nothing else. Cold-inlet climates are where electric tankless disappoints people.

Check price on Amazon

No live price feed on this site, so we show none. #ad

Specifications above from Stiebel Eltron Tempra Plus technical specifications (PDF); Stiebel Eltron Tempra Plus submittal sheet (PDF). We have not tested this unit ourselves.

What EcoSmart does well

• A lifetime limited warranty on the ECO 27, which is unusual at any price in this category.
• Genuine physical compactness. The ECO 27 is 17 by 17 by 3-5/8 inches and weighs 14.7 pounds. It disappears on a wall.
• 0.3 GPM activation flow on the ECO 27, the lowest in our registry, so a trickle at a faucet still fires it.
• An honest published flow range on the ECO 11 — 1.3 to 3.2 GPM, explicitly tied to inlet temperature. That is a more useful statement than a bare maximum.
• Self-modulating control and a digital set point in 1°F increments.

Where it falls short

• No rise-versus-flow table on the ECO 27. The 6.6 GPM figure is a maximum with no stated rise, so you cannot check it against your own inlet temperature. Stiebel Eltron publishes a four-point curve at two voltages, and that is why the Tempra ranks above the ECO 27 in our electric roundup.
• The electrical requirement is the product's real limit, and it is stated in the spec sheet rather than the marketing.
• No buffer or flow control, so a sudden flow change is felt at the shower head rather than absorbed.
• Thinner service network than a brand with national wholesale distribution behind it.

Which EcoSmart, honestly

Our verdict

The ECO 11 is a genuinely useful product and the one we would point most people at: one circuit, a real published flow range, and it solves the distant-fixture problem without a service upgrade.

The ECO 27 is capable hardware let down by documentation. If you need maximum electric output and have the service for it, it works and the lifetime limited warranty is attractive. If you want to size an electric tankless unit from published data, buy the Stiebel Eltron instead. Best electric tankless water heaters.