Head-to-head · Best Tankless Water Heaters

EcoSmart ECO 27 vs Stiebel Eltron Tempra 36 Plus

Which is the better buy? Side-by-side on rating, price, strengths, and watch-outs — with the published ratings we averaged to get there.

The short answer

Stiebel Eltron Tempra 36 Plus comes out ahead by a narrow margin (4.2 vs 4.4). The gap is mostly about All-electric homes in moderate climates that need whole-house hot water without gas or venting. — read the strengths below before deciding.

Ranked #4 in Best Tankless Water Heaters

EcoSmart ECO 27

4.2

$466.24as of Jun 7

The EcoSmart ECO 27 is the efficient electric value pick — a 27 kW self-modulating unit that This Old House rated 4.3/5 for the EcoSmart line, praising that it 'can save you up to 50% on your water-heating bill thanks to its self-modulating temperature control.' It delivers up to 6.5 GPM in warm climates, enough for a small whole home, from a compact wall-mounted box with precise digital temperature control. Its flow drops in cold-inlet regions and it needs substantial electrical service, but for warm-climate homes it's a strong, affordable electric option.

Strengths

— Self-modulating technology uses only the energy needed
— Up to 6.5 GPM in warm climates, enough for small whole-home use
— Compact 17 x 17 x 3.5-inch wall-mounted footprint

Watch-outs

— Flow rate drops sharply in cold-inlet climates (down to ~2.7 GPM)
— 27 kW draw requires significant electrical service
— Best suited to warm regions or smaller homes

$466.24 · Check Price on Amazon Full review →

Higher ratedRanked #2 in Best Tankless Water Heaters

Stiebel Eltron Tempra 36 Plus

4.4

$789.11as of Jun 7

The Stiebel Eltron Tempra 36 Plus is the clear frontrunner for whole-home electric tankless heating, delivering up to 7.5 GPM from its 36 kW heating element. This Old House rated the Stiebel Eltron electric line 4.4/5, and Bob Vila named it best electric, both praising its silent operation and standout Advanced Flow Control, which dynamically reduces flow rather than letting cold-water sandwiching occur when demand exceeds capacity. It needs serious electrical service and performs best in moderate climates, but for an all-electric home it is the top whole-house pick.

Strengths

— Best whole-home electric option, up to 7.5 GPM at 36 kW
— Advanced Flow Control throttles flow to prevent cold-water sandwiching
— Silent operation with no combustion, venting, or CO risk

Watch-outs

— Needs substantial electrical service — often a panel upgrade
— Flow rate drops in cold climates with high temperature rise
— No federal gas tax credit (electric)

$789.11 · Check Price on Amazon Full review →

How they stack up

EcoSmart ECO 27

The EcoSmart ECO 27 is the mid-tier electric option, more affordable than the whole-home Stiebel Eltron Tempra 36 Plus but with lower and more climate-dependent flow (2.7-6.5 GPM). It lacks the Stiebel's Advanced Flow Control. It outflows the point-of-use Rheem RTEX-13 but, like all electric units here, trails the gas Rinnai RU199iN and Takagi T-H3-DV-N.

Stiebel Eltron Tempra 36 Plus

The Stiebel Eltron Tempra 36 Plus is the best whole-home electric unit, with a 7.5 GPM flow rate that beats the EcoSmart ECO 27 and Rheem RTEX-13 but trails the gas Rinnai RU199iN and Takagi T-H3-DV-N. Its Advanced Flow Control is a feature neither the EcoSmart nor the Rheem offers, trading a brief flow reduction for consistently hot water.

Specs side-by-side

Spec	EcoSmart ECO 27	Stiebel Eltron Tempra 36 Plus
Fuel	Electric	Electric
Power	27 kW	36 kW
Flow Rate	2.7 - 6.5 GPM (climate-dependent)	Up to 7.5 GPM
Control	Self-modulating, digital (1-degree)	Advanced Flow Control + self-modulating
Dimensions	17 x 17 x 3.5 in	—
Venting	None required	None required
Mounting	Wall-mounted	Wall-mounted
Best Climate	Warm / southern U.S.	—
Voltage	—	240/208V
Origin	—	Made in Germany

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