EcoSmart ECO 27 27kW Electric Tankless Water Heater

The EcoSmart ECO 27 27kW Electric Tankless Water Heater is the largest residential electric tankless on the US market — and the unit that owns the budget-tier electric-tankless category. About 4,800 monthly searches for "ecosmart tankless water heater" land on this exact model. 6 GPM peak flow (35°F rise). 0.99 UEF (electric tankless is theoretically near-perfect efficiency). $549–$649 typical pricing. Self-modulating power draw via the ECO digital controller. The right pick for whole-house electric tankless in warm-water-supply regions, single-bathroom installs in cold regions, and any scenario where a gas tankless isn't viable.

Headline specifications

• Type: electric tankless, point-of-entry or point-of-use
• Power: 27,000 watts (3 × 9kW elements, modulating)
• Electrical service required: 200-amp panel minimum, 3 × 40-amp dedicated 240V circuits
• Maximum flow rate: 6.0 GPM at 35°F rise (lower in colder inlet water)
• Minimum activation flow: 0.3 GPM
• Energy Factor (UEF): 0.99
• Temperature range: 80°F – 140°F adjustable via digital controller
• Warranty: Lifetime on heat exchanger, 5-year on electronics
• Dimensions: 17" H × 17" W × 3.625" D — about the size of a small wall safe
• Weight: 14 lbs

Who this model is for

The ECO 27 is calibrated for whole-house electric tankless in regions where the inlet water temperature stays above 60°F most of the year. That's most of the Sun Belt (Florida, Texas, Arizona, Southern California, Gulf Coast). In those regions, the 27 kW power can heat 6 GPM with a 35°F rise — adequate for 2 simultaneous showers or one shower plus a kitchen sink.

In cold-climate regions (Northeast, Midwest, Mountain West) where inlet water can hit 40°F in winter, the same 27 kW unit only handles 3.5–4 GPM at the required 75°F rise. For those regions the ECO 27 still works for single-bathroom or supplemental use, but a gas tankless or larger electric installation is needed for whole-house demand.

It's also the right pick for buyers without gas service who can't justify a heat-pump install (no install space, no condensate drain, or specific use cases where the heat pump's slow recovery is unacceptable). The tankless eliminates the standby loss of an electric tank and the install footprint shrinks to about the size of a wall safe.

Common practical applications:

• Whole-house replacement in warm-water-supply regions (Florida, Texas, etc.)
• Single-bathroom upgrade or addition in cold-supply regions
• Workshop, garage apartment, or auxiliary unit hot water
• Off-grid solar+electric installations where running cost matters less than install simplicity
• Replacement for a small electric tank that keeps running out of hot water

The electrical requirement reality

The single biggest hurdle to ECO 27 installation is the electrical panel. 27,000 watts at 240V draws 112 amps — three dedicated 40-amp double-pole circuits. Most US homes have 100–200 amp panels. After the existing house loads, finding 112 amps of available capacity is the typical limiter:

• 200-amp panel: usually feasible after a load calculation. Some loads (electric dryer, range, oven, central AC) overlap the water heater's draw and the calculation works out.
• 100-amp panel: almost never feasible without a service upgrade ($1,500–$3,500).
• Subpanel installation may be required even on 200-amp service to provide the three dedicated 40-amp circuits.

Get an electrician's load calculation before purchase. The ECO 27 spec sheet looks small ($549!) but the electrical work to support it can add $1,200–$4,000 depending on existing panel capacity.

Where it beats the alternatives

Vs Stiebel Eltron Tempra 36 Plus ($949–$1,149): the Tempra is the premium German alternative at 36 kW. Higher flow capacity (7.5 GPM at 35°F rise), better controls, and a quieter modulation algorithm. But $400+ more upfront. For warm-water-supply regions, the ECO 27 at 6 GPM is adequate and the savings are significant.

Vs Marey ECO270 ($399–$499): Marey is the value-tier electric tankless. Similar 26 kW power, lower price, shorter warranty, less polished controls. For tight budgets, Marey works. For most buyers, the ECO 27's better controls and lifetime heat exchanger warranty are worth the $150 premium.

Vs Eemax HA036240 ($1,099–$1,299): Eemax is now Rheem-owned and competes at the premium electric tankless tier. 36 kW capacity, 7-year warranty. The ECO 27 is the value pick at half the price for buyers who don't need the extra capacity.

Vs gas tankless (Rinnai RU199iN, etc.): if you have natural gas service, gas tankless is dramatically better. Higher flow capacity, faster recovery, lower operating cost in most regions. The ECO 27 wins only when gas isn't available or the install scope of running new gas line + venting makes gas impractical.

Vs electric tank ($499 for a standard 50-gallon): roughly the same upfront cost, but the tankless eliminates the standby loss (the constant ~15–20% of energy that keeps a tank at temperature even when no hot water is being used) and the 8–12 year tank-failure replacement event. For long-horizon owners, tankless wins on lifecycle math.

Where it falls short

6 GPM peak flow is the ceiling. Run a long shower (2.5 GPM) plus a kitchen sink on hot (2 GPM) plus a clothes washer warm cycle (1.5 GPM) and the unit can keep up. Add another simultaneous demand and the temperature output drops. Households with high simultaneous demand need to size up or accept that pure simultaneous loads aren't feasible.

Cold-inlet water performance. Electric tankless flow capacity is governed by power × temperature rise. At 35°F rise (Sun Belt summer), 27 kW handles 6 GPM. At 75°F rise (Northeast winter), the same 27 kW handles only 3.5 GPM. Plan capacity for your worst-case winter inlet, not the summer average.

Electrical service is the binding constraint. See above. The ECO 27's bargain price disappears fast if your panel needs upgrades.

5-year electronics warranty — the heat exchanger has a lifetime warranty but the modulating electronics carry only 5 years. Beyond that, control board failure is the failure mode that typically ends the unit's life.

Self-modulation has a learning curve. The unit adjusts power based on flow and inlet temperature in real time, but it takes a few seconds to settle when you open or close additional fixtures. Briefly fluctuating temperature during multi-fixture use is normal.

Install considerations

Get an electrician's load calculation first. Required before purchase. The electrical scope determines whether this is a $700 install or a $3,500 install.

Three dedicated 40-amp 240V circuits. 8 AWG copper minimum. Each circuit feeds one of the three 9 kW elements.

Water connections: 3/4" NPT cold inlet and hot outlet. The unit mounts on a wall — no floor footprint.

Permit: required in most US jurisdictions. The electrical work must pass inspection.

Plumber-installable: the water plumbing is straightforward. The electrical wiring requires a licensed electrician in most jurisdictions.

Install cost: $700–$1,200 for a straightforward install with existing capacity; $2,500–$4,000 if panel/service upgrades are required.

Maintenance

• Inlet filter clean every 6 months — removes sediment before it hits the heating elements
• Annual descaling in hard-water regions — flush the heat exchanger with white vinegar via the included service valves (if installed)
• Element inspection at year 5 and year 10 — visual check for scale or corrosion

Bottom line

The EcoSmart ECO 27 is the right pick for whole-house electric tankless in warm-water-supply regions, single-bathroom electric tankless in cold-supply regions, and any scenario where the install scope doesn't allow gas or heat-pump alternatives. The unit price is genuinely bargain at $549–$649, but the electrical service requirement is the binding constraint that determines whether the total install cost stays reasonable. Buyers with 200-amp service and existing capacity get extraordinary value; buyers with 100-amp panels should factor service-upgrade costs before committing. For buyers with natural gas service, a gas tankless or gas tank is almost always the better choice. Click through to Amazon for live pricing; get an electrician's load calculation before purchase.