Tankless Water Heater Reviews (2026): 4 Gas and Electric Models Scored

In these tankless water heater reviews we score four models, two high-output electric units, a mid-size gas unit and a point-of-use heater, on the things that matter after installation: real flow for your household, efficiency, temperature control and how demanding the install is.

All four were scored on the same criteria using manufacturer specifications and owner feedback. For our main shortlist see the best tankless water heater guide; our Editorial Policy explains how we work.

Top 3 Tankless Water Heaters From Our Reviews

Highest Overall Score

Rheem RTG-84DVLN-3 8.4 GPM Natural Gas Tankless Water Heater (Indoor)

• 8.4 GPM
• Gas
• Hot-start

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Best Electric

Rheem RTEX-27 27kW 240V Electric Tankless Water Heater

• 27kW
• Serviceable
• LED control

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Best Electric Flow

EcoSmart ECOS 27 27kW 240V Electric Tankless Water Heater

• 6.6 GPM
• 27kW
• Compact

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How We Scored Tankless Water Heaters

Tankless Water Heaters Compared

#	Product	Key Features
1	Rheem RTG-84DVLN-3 8.4 GPM Natural Gas Tankless Water Heater (Indoor)	8.4 GPM 180,000 BTU 1/2″ gas line compatible	Check Latest Price
2	Rheem RTEX-27 27kW 240V Electric Tankless Water Heater	27kW 3 copper elements Self-modulating	Check Latest Price
3	EcoSmart ECOS 27 27kW 240V Electric Tankless Water Heater	27kW Up to 6.6 GPM ±1° control	Check Latest Price
4	Stiebel Eltron DHC-E 8/10 Classic Point-of-Use Tankless Water Heater	7.2kW Booster ready Copper chamber	Check Latest Price

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1. Rheem RTG-84DVLN-3 8.4 GPM Natural Gas Tankless Water Heater (Indoor)

Highest Overall Score: 8.9/10

Pros

• 8.4 GPM at a 35°F rise
• 180,000 BTU for 3–4 showers
• Works with 1/2″ gas line in many installs (per Rheem)
• Hot-start programming and leak protection
• UEF 0.82

Cons

• Non-condensing
• Natural gas indoor version

• Fuel: natural gas
• Flow: 8.4 GPM
• Model: RTG-84DVLN-3

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The RTG 8.4 GPM scored highest because it gives whole-house flow with less demanding gas line requirements than larger units.

Hot-start programming reduces the cold-water sandwich between uses.

Who the Rheem RTG 8.4 GPM fits best

Most 2–3 bathroom homes on gas.

Who should skip the Rheem RTG 8.4 GPM

Propane homes.

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2. Rheem RTEX-27 27kW 240V Electric Tankless Water Heater

Best Electric: 8.7/10

Pros

• 27kW, three copper immersion elements
• Advanced self-modulation
• External digital control, ±1° accuracy
• Field-serviceable elements

Cons

• Needs about 112A of breaker capacity
• Large panel required

• Power: 27kW, 240V
• Water: 3/4″ NPT bottom
• Model: RTEX-27

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The RTEX-27 is the strongest electric unit here and its elements can be replaced in the field.

Have an electrician confirm panel capacity first.

Who the Rheem RTEX-27 fits best

Large electric homes.

Who should skip the Rheem RTEX-27

Homes with limited service.

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3. EcoSmart ECOS 27 27kW 240V Electric Tankless Water Heater

Best Electric Flow: 8.5/10

Pros

• 27kW, up to 6.6 GPM
• Self-modulating, within 1° of setting
• Compact 19 x 4.25 x 9.25 inches
• 96% thermal efficiency

Cons

• 112.5A draw
• Flow drops in cold climates

• Power: 27kW, 240V
• Flow: up to 6.6 GPM
• Model: ECOS 27

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EcoSmart’s ECOS 27 is slim enough to fit in a closet and handles two showers in warm regions.

Its temperature holds steady thanks to flow monitoring.

Who the EcoSmart ECOS 27 fits best

Electric homes needing compact install.

Who should skip the EcoSmart ECOS 27

Northern climates.

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4. Stiebel Eltron DHC-E 8/10 Classic Point-of-Use Tankless Water Heater

Best Point-of-Use: 8.1/10

Pros

• 7.2kW at 240V
• Microprocessor controls, no scalding
• Accepts preheated water up to 131°F for booster use
• Solid copper heating chamber

Cons

• Single fixture only
• Hardwired

• Power: 7.2kW, 240V
• Model: DHC-E 8/10 Classic
• Use: point-of-use or booster

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The DHC-E 8/10 is for one sink or shower far from the main heater, or as a booster after solar or tank systems.

It removes the wait at a distant fixture.

Who the Stiebel Eltron DHC-E 8/10 fits best

Remote sinks or boosting.

Who should skip the Stiebel Eltron DHC-E 8/10

Whole-house use.

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Tankless Water Heater Buying Checklist

• Measure fixtures used at once and your incoming water temperature.
• Confirm panel amps for electric units or gas line size for gas units.
• Plan venting and condensate for gas models.
• Budget for professional installation and yearly flushing.

Frequently Asked Questions

Which tankless water heater scored highest?

The Rheem RTG 8.4 GPM scored 8.9/10.

Is 27kW enough for a whole house?

In warm climates, often 2 showers; colder areas need more.

Do point-of-use heaters save energy?

They cut wait time and pipe heat loss at distant fixtures.

How often should I flush?

Once a year, or more with hard water.

Final Verdict: Tankless Water Heater Reviews

The Rheem RTG 8.4 GPM is the best tankless water heater we scored. The Rheem RTEX-27 is the best electric model, and the EcoSmart ECOS 27 offers the best electric flow.

Match flow and power to your home, and install it right.

Looking for something else? Browse all of our Water Heaters guides and the wider Heating & Cooling section.

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