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.
Full review
Efficient Electric Heating
The EcoSmart ECO 27's calling card is efficiency. Its self-modulating technology draws only the power needed to hit the set temperature, and This Old House, which rated the EcoSmart line 4.3/5, noted it 'can save you up to 50% on your water-heating bill thanks to its self-modulating temperature control.' Reviewed described it the same way: 'designed to self-regulate, using only the energy needed to heat the water when you need it.' Unlike a tank that keeps water hot around the clock, the ECO 27 heats on demand, which is where the savings come from.
Flow Rate and Climate
At 27 kW the ECO 27 can deliver up to 6.5 GPM — enough, per Amazon's listing, for 'larger homes in warm climates' or 'small whole home applications.' The crucial caveat is climate: the same listing notes it provides 'between 2.7 and 6.5 gallons-per-minute depending on the inlet water temperature.' In the warm South, where groundwater enters relatively warm, it delivers near its top flow; in cold northern winters, where it must raise frigid water many degrees, that figure can fall toward 2.7 GPM. Matching the unit to your climate is essential, which is why professionals steer electric tankless buyers toward warmer regions.
It lacks the Stiebel Eltron Tempra 36 Plus's Advanced Flow Control, so under extreme simultaneous demand it can't throttle flow to preserve temperature the way the Stiebel does.
Compact, Simple Design
The ECO 27 is small — a 17 x 17 x 3.5-inch box that mounts on a wall and frees up the floor space a tank would occupy. It uses precise digital temperature control adjustable in single-degree increments, so you can dial in exactly the output you want. Being electric, there's no venting, no gas line, and no carbon-monoxide risk, which keeps installation cleaner than a gas unit, though the 27 kW draw still requires heavy electrical service.
What Reviewers Loved
This Old House's 'most efficient' framing and Reviewed's praise for its self-regulation both center on the same strength: it sips power and saves money relative to a tank. Reviewers also appreciate the compact footprint and the precise digital control. At its price point, it's repeatedly cited as a strong value for buyers who don't need the absolute maximum flow.
Where It Falls Short
The ECO 27's biggest limitation is climate sensitivity — its flow rate falls significantly in cold-inlet regions, so a northern household may find it can't keep up with multiple fixtures in winter. The 27 kW draw demands substantial electrical service, often requiring upgrades. It lacks the Stiebel's anti-cold-sandwich flow control, and as an electric unit it doesn't qualify for the gas tankless federal tax credit. It's a warm-climate or small-home solution, not a cold-climate whole-home one.
Who It's Best For
The EcoSmart ECO 27 is the right pick for a warm-climate home that wants an efficient, affordable, compact electric tankless unit for small whole-home use. It's a strong value if your inlet water is reasonably warm and your simultaneous demand is moderate. If you're in a cold climate or need guaranteed whole-home flow, step up to the Stiebel Eltron Tempra 36 Plus or a gas unit; if you only need hot water at one location, the cheaper Rheem RTEX-13 is plenty.
Value at This Price
The ECO 27 is one of the better-value electric units in this group, priced well below the Stiebel Eltron Tempra 36 Plus while offering meaningful whole-home capability in the right climate. This Old House's 'most efficient' framing captures the long-term case: the self-modulating element and tankless on-demand operation can cut water-heating costs by up to 50% versus a tank. The honest caveat is that its value is climate-bound — in a warm southern home it's a near-ideal balance of price, footprint, and capacity, but in a cold-inlet region its falling flow rate undercuts the savings and pushes you toward the Stiebel or a gas unit. Match it to a warm climate and it's one of the smartest-spending picks here; mismatch it to a cold one and you'll be disappointed.
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
- +Digital temperature control in 1-degree increments
- +No venting, no gas, no carbon-monoxide risk
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
- −No federal gas tax credit (electric)
How it compares
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.
Who this is for
At a glance: Warm-climate homes wanting an efficient, affordable electric unit for small whole-home use.
Why you’d buy the EcoSmart ECO 27
- 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.
Why you’d skip it
- 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.
Rating sources
“can save you up to 50% on your water-heating bill thanks to its self-modulating temperature control”
“designed to self-regulate, using only the energy needed to heat the water when you need it”
“ideal for providing hot water for larger homes in warm climates, between 2.7 and 6.5 gallons-per-minute depending on the inlet water temperature”
Our 4.2 score is the average of these published ratings. Ratings marked * were derived from the reviewer’s written analysis or video transcript — the publisher didn’t print an explicit numeric score, so we inferred one from their own words. Click through to verify. More about methodology.
