Best Electric Tankless Water Heaters

Electric tankless is a genuinely good product being sold for the wrong job. At one fixture, or in a warm-inlet climate, or as a point-of-use unit at a distant sink, it is excellent: no venting, no gas, no condensate, and it disappears into a cabinet. As a whole-house heater in a northern winter, it asks for electrical service most houses do not have and still delivers one shower.

The electrical requirement, up front

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	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
2	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
3	Rheem Professional Classic RTEX-24The value electric unit: 24 kW, 5.9 GPM rated flow and a digital set point in 1°F steps, from a brand whose parts your local supply house actually stocks.	Electric tankless on a budget	Check price on Amazon No live price feed on this site, so we show none. #ad
4	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

The picks in full

Pick 1 — 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.

Pick 2 — 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 3 — Electric tankless on a budget

Rheem Professional Classic RTEX-24

The value electric unit: 24 kW, 5.9 GPM rated flow and a digital set point in 1°F steps, from a brand whose parts your local supply house actually stocks.

Published specifications for the Rheem Professional Classic RTEX-24

Output	24 kW at 240 V
Rated flow	5.9 GPM
Breakers	3 x 40 A
Service required	200 A
Thermal efficiency	99.8%
Set point range	80 - 140°F in 1°F increments

What is good

• +Parts and warranty support through a brand with national distribution
• +Digital set point in single degrees rather than a notched dial
• +99.8% thermal efficiency: effectively all the electricity lands in the water
• +Cheaper than the German-built alternatives at the same kW

What is not

• −Rheem quotes a rated flow rather than a published rise-versus-flow curve
• −Three 40 A circuits and a 200 A service requirement
• −No flow control, so high flow shows up as lower temperature

Skip it if: Skip it if you want to size from published data. Rheem lists a rated GPM without the temperature rise it was measured at, so you cannot check the number against your own inlet temperature the way you can with the Tempra.

Check price on Amazon

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Specifications above from Rheem RTEX-24 / RTEX-27 product page; Pace Supply listing, RTEX-24, 240 V 24 kW 100 A. We have not tested this unit ourselves.

Pick 4 — 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

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

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

Why the Tempra ranks first despite lower output

Because it tells you the truth. Stiebel Eltron publishes maximum temperature rise at four flow rates, on both 240 V and 208 V supply. That single table lets you check the unit against your own inlet temperature before you buy it, which no amount of headline GPM does.

It also has Advanced Flow Control, which throttles the flow to hold the set temperature rather than delivering lukewarm water at a higher flow. That is the right failure mode: a slightly weaker shower rather than a cold one.

The 208 volt problem nobody mentions

A great many American homes and apartments sit nearer 208 V than 240 V, particularly in multi-family buildings. At 208 V the Tempra 24 Plus produces 18 kW instead of 24, and its maximum rise at 3.00 GPM falls from 54°F to 41°F. That is the difference between a usable shower and a disappointing one.

Measure your actual supply voltage at the panel before you size an electric tankless unit. If it is 208 V, size from the 208 V column, every time.

Where electric tankless is the right answer

• A single distant bathroom where running a gas line is impossible and the wait for hot water is the complaint. An ECO 11 on one 60 A circuit solves it.
• A warm-inlet climate where a 50 to 55°F rise is all you need. A 24 kW unit at 3.00 GPM and a 54°F rise is a real whole-house heater in south Florida.
• An addition, an ADU or a garage apartment with no gas service and a modest hot water demand.
• A remodel where the water heater's floor space is genuinely valuable and the electrical work is happening anyway.

Where it is the wrong answer

• A northern whole-house retrofit. At a 73°F rise the Tempra 24 Plus gives 2.25 GPM. One shower.
• A 100 A or 125 A panel. Three 40 A circuits and 113 A of draw is a service upgrade, and that usually costs more than the entire water heater.
• A household wanting two simultaneous showers in a cold climate. This is the gas tankless use case, or a tank.
• Anywhere the electric rate is high and usage is heavy. Resistance heating is resistance heating; a heat pump water heater is three to four times more efficient at the same job.

How we chose

We ranked honest published data first — a unit whose rise-versus-flow curve you can check is more useful than one with a bigger headline number. Then electrical realism, then warranty, then parts availability. We have not tested these units. How we pick.