Head-to-head · Best Tankless Water Heaters

EcoSmart ECO 27 vs Rheem RTEX-13

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

EcoSmart ECO 27 comes out ahead by a narrow margin (4.2 vs 4.1). The gap is mostly about Warm-climate homes wanting an efficient, affordable electric unit for small whole-home use. — read the strengths below before deciding.

Higher ratedRanked #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 →

Ranked #5 in Best Tankless Water Heaters

Rheem RTEX-13

4.1

$278as of Jun 7

The Rheem RTEX-13 is the best bang-for-the-buck pick — Bob Vila's value choice and Reviewed's budget electric unit, praised for a '99 percent efficiency rating' at the lowest price in this group. With about 3.17 GPM it's a point-of-use heater designed, as Reviewed notes, 'to support one to two appliances in a single location, such as a shower in the bathroom.' It won't run a whole house, but for a remote bathroom, an addition, or as a booster, its compact size, efficiency, and low cost make it the obvious affordable choice.

Strengths

— Lowest price of the group — excellent point-of-use value
— Roughly 99% energy efficiency with self-modulating control
— Compact 13 kW unit easy to install near a single fixture

Watch-outs

— Only ~3.17 GPM — supports one to two fixtures, not a whole home
— Not suitable as a primary whole-house heater in most homes
— Flow drops further with cold inlet water

$278 · 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.

Rheem RTEX-13

The Rheem RTEX-13 is the smallest and cheapest unit here, a point-of-use heater at about 3.17 GPM versus the whole-home flow of the Stiebel Eltron Tempra 36 Plus and EcoSmart ECO 27, and far below the gas Rinnai RU199iN and Takagi T-H3-DV-N. It's not a whole-home replacement, but it's the value leader for single-fixture jobs.

Specs side-by-side

Spec	EcoSmart ECO 27	Rheem RTEX-13
Fuel	Electric	Electric
Power	27 kW	13 kW
Flow Rate	2.7 - 6.5 GPM (climate-dependent)	Up to ~3.17 GPM
Control	Self-modulating, digital (1-degree)	Self-modulating, digital readout
Dimensions	17 x 17 x 3.5 in	—
Venting	None required	None required
Mounting	Wall-mounted	—
Best Climate	Warm / southern U.S.	—
Efficiency	—	~99%
Voltage	—	240V
Use	—	Point-of-use / single fixture

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