Top 10 Tankless Water Heaters in 2027 — Best Overall + Best Value

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How We Ranked the Top 10

We weighted real-world performance over spec-sheet bragging rights, leaning on hands-on testing and teardown reporting from This Old House, Bob Vila, Consumer Reports, Popular Mechanics, and Forbes Home, then cross-checked GPM, UEF, and BTU figures against manufacturer spec sheets from Rinnai, Navien, Rheem, EcoSmart, and Stiebel Eltron.

• Flow rate (GPM) & capacity — 25%
• Energy efficiency (UEF, condensing) — 20%
• Gas vs electric fit — 15%
• Reliability & warranty — 15%
• Install & venting — 15%
• Price-to-performance — 10%

1. Rinnai RX199iN Sensei 🏆 BEST OVERALL

Rinnai RX199iN Sensei

Price: $1,700 | Best for: Large gas-line homes that want maximum flow and the longest life

The Rinnai RX199iN Sensei is a condensing natural-gas unit rated at 11.1 GPM and a class-leading 0.98 UEF, fed by up to 199,000 BTU of input. It installs indoors or outdoors with PVC venting and pairs to the Rinnai Central app for temperature scheduling and diagnostics. With annual descaling, master plumbers expect this unit to run 18 to 20 years, and it ships with a 15-year heat-exchanger warranty. It is the unit we would put in our own house.

Pros:

• Highest practical flow at 11.1 GPM for multiple showers at once
• 0.98 UEF condensing efficiency trims gas bills
• Wi-Fi app control and outdoor-rated versatility
• 15-year heat-exchanger warranty

Cons:

• Premium price before install
• Requires annual descaling in hard-water areas

Verdict: The best all-around tankless heater for gas homes that want flow, efficiency, and longevity in one box.

2. Navien NPE-240A2

Navien NPE-240A2

Price: $1,450 | Best for: Homes wanting built-in recirculation for faster hot water

The Navien NPE-240A2 is an ultra-high-efficiency condensing gas unit that delivers up to 11.2 GPM at a 35°F rise, with input ranging from 13,300 to 199,900 BTU and a 0.95 UEF. Its standout feature is built-in recirculation, which cuts the wait for hot water at distant fixtures without a separate pump. Dual stainless heat exchangers are rated to last up to 25 years, and Navien backs it with one of the strongest warranties in the category.

Pros:

• Built-in recirculation for near-instant hot water
• 11.2 GPM peak flow rivals the class leader
• Stainless exchangers rated up to 25 years
• ENERGY STAR efficiency

Cons:

• Slightly lower UEF than the Rinnai Sensei
• Condensate drain and venting add install complexity

Verdict: The smartest pick when fast hot water at far-flung faucets matters as much as raw flow.

3. EcoSmart ECO 27

EcoSmart ECO 27

Price: $580 | Best for: Warm-climate homes that want whole-home hot water without gas

The EcoSmart ECO 27 is a 27 kW electric whole-home unit that supplies a single-family house with steady, unlimited hot water at up to 6.6 GPM in sunnier climates and roughly 3 GPM at the coldest incoming groundwater. Self-modulating technology draws only the power needed, copper and stainless internals resist scale, and EcoSmart backs the elements with a lifetime warranty. There is no venting, no gas line, and a compact wall-mount footprint.

Pros:

• No gas, no venting — simple electric install
• Self-modulating power draw saves energy
• Lifetime warranty on heating elements
• Low $580 price for whole-home capacity

Cons:

• Needs 200-amp service and heavy-gauge wiring
• Flow drops sharply in cold-groundwater regions

Verdict: The best value in the category for warm-climate homes ready to skip gas entirely.

4. Rheem RTEX-36 💎 BEST VALUE

Rheem RTEX-36

Price: $680 | Best for: Whole-home electric buyers who want field-serviceable reliability

The Rheem RTEX-36 is a 36 kW electric whole-home unit and a top-tier electric pick for its field-serviceable design — replaceable elements and a digital thermostat make repairs a screwdriver job rather than a callout. It holds steady output even in cooler climates better than lower-wattage electrics, backed by Rheem's proven reliability and a long element warranty. For buyers who want electric simplicity plus the ability to fix it themselves, the dollar-per-capacity math is hard to beat.

Pros:

• Field-serviceable replaceable elements
• 36 kW handles cooler groundwater than smaller units
• Digital temperature control in 1°F steps
• Rheem reliability at an electric price

Cons:

• Demands a heavy electrical-panel upgrade
• Outsized for small or warm-climate homes

Verdict: The best value for whole-home electric buyers who refuse to be held hostage by service calls.

5. A.O. Smith Signature Series Super High Efficiency

A.O. Smith Signature Series Super High Efficiency

Price: $1,250 | Best for: Big households on gas wanting brand support at a fair price

The A.O. Smith Signature Series condensing gas unit delivers up to 10.6 GPM on 180,000 to 199,000 BTU, with indoor-outdoor natural-gas or propane operation. It pairs strong real-world flow with A.O. Smith's deep retailer and parts network, so support and replacement components are easy to find. Efficiency lands in the condensing range, and venting uses standard PVC.

Pros:

• 10.6 GPM for large simultaneous demand
• Natural-gas or propane flexibility
• Wide parts and service availability
• Mid-tier price for a high-output unit

Cons:

• Slightly lower flow than the Rinnai and Navien leaders
• App features lag the smartest competitors

Verdict: A dependable high-flow gas unit for big households that value easy support over bleeding-edge features.

6. Takagi T-H3-DV-N

Takagi T-H3-DV-N

Price: $500 | Best for: Bargain gas buyers comfortable with a discontinued-but-supported line

The Takagi T-H3-DV-N is a condensing natural-gas indoor unit rated at 10 GPM on 199,000 BTU with ultra-low-NOx combustion. At around $500 for the unit, it is one of the cheapest ways into real high-output gas tankless performance. Note that Takagi discontinued the line at the end of 2025, so new stock is closeout inventory — fine if you value price and can source parts, less ideal if you want long-term factory backing.

Pros:

• 10 GPM high-output gas at a bargain price
• Condensing, ultra-low-NOx combustion
• Compact indoor wall-mount design
• Around $500 unit cost

Cons:

• Line discontinued as of December 2025
• Future parts support is a question mark

Verdict: A genuine high-flow gas unit at a closeout price for buyers who prize value over warranty longevity.

7. Stiebel Eltron Tempra 36 Plus

Stiebel Eltron Tempra 36 Plus

Price: $815 | Best for: Electric homes wanting the best temperature precision

The Stiebel Eltron Tempra 36 Plus is the frontrunner for whole-home electric heating in 2027, prized for its advanced flow control that holds output temperature rock-steady even as demand changes. It is a 36 kW unit with a strong real-world flow and a clean German-engineered build. Stiebel Eltron backs it with a 10-year combined warranty, and at roughly $815 it sits above bargain electrics but earns it in control quality.

Pros:

• Best-in-class temperature stability under load
• 36 kW whole-home electric capacity
• 10-year combined warranty
• Quiet, compact, no venting

Cons:

• Pricier than the EcoSmart and Rheem electrics
• Requires substantial electrical service

Verdict: The electric pick for buyers who hate temperature swings and will pay a little more for steady showers.

8. Rinnai RX130iN Sensei

Rinnai RX130iN Sensei

Price: $1,150 | Best for: Smaller gas homes that want Rinnai quality without paying for max flow

The Rinnai RX130iN Sensei scales the Best Overall winner's platform down for smaller households, delivering ample flow for one to two simultaneous fixtures on a condensing gas design. It keeps the same app control, build quality, and reliability reputation as its bigger sibling, at a meaningfully lower price. For a couple or a two-bath home that does not need 11 GPM, this is the right-sized Rinnai.

Pros:

• Right-sized flow for small homes saves money
• Same Rinnai app and build quality
• Condensing efficiency with PVC venting
• Lower entry price than the flagship

Cons:

• Not enough flow for large simultaneous demand
• Still needs annual descaling in hard water

Verdict: The value-minded Rinnai for smaller gas homes that want the brand without the flagship price.

9. EcoSmart ECO 11

EcoSmart ECO 11

Price: $230 | Best for: Point-of-use jobs — a single sink, shower, or remote bathroom

The EcoSmart ECO 11 is a 13 kW, 240-volt electric point-of-use unit rated at 2.54 GPM, designed to serve one or two fixtures right where they are used. It carries up to a 0.96 UEF with self-modulating copper immersion elements, mounts in a tiny footprint, and needs a double-pole 60-amp breaker with 6-gauge wire. It is the answer for a garage sink, a workshop, or a far-corner bathroom that the main heater serves slowly.

Pros:

• Point-of-use instant hot water at the fixture
• 2.54 GPM plenty for a sink or single shower
• Up to 0.96 UEF self-modulating efficiency
• Tiny $230 price and footprint

Cons:

• Single-fixture capacity only, not whole-home
• Needs a dedicated 60-amp circuit

Verdict: The go-to point-of-use unit for adding fast hot water to one isolated fixture cheaply.

10. Bosch Tronic 3000 US3-2R

Bosch Tronic 3000 US3-2R

Price: $160 | Best for: Under-sink installs where you just need warm water fast and cheap

The Bosch Tronic 3000 US3-2R is a 3.6 kW electric under-sink unit that fits behind a vanity to take the cold-water lag out of a single lavatory. It is not a whole-home or shower unit — it is a small, plug-in-simple booster that warms water for handwashing and light tasks at the point of use. At roughly $160, it is the cheapest, easiest tankless on the list and a smart fix for a sink far from the main heater.

Pros:

• Lowest price on the list at $160
• Compact under-sink fit behind a vanity
• Simple low-amp electrical install
• Eliminates cold-water lag at a single sink

Cons:

• Low 3.6 kW output — handwashing duty only
• Not suitable for showers or multiple fixtures

Verdict: The cheapest, simplest way to kill cold-water lag at one bathroom sink.

Buyer Decision Tree — Which One's Right for You?

What to Look For When Buying a Tankless Water Heater

• GPM flow for your household and climate — Cold groundwater forces a bigger temperature rise, which drops effective flow. Size for the coldest month, not the warmest, and add up the fixtures you run at once.
• Gas vs electric and capacity — Gas units hit 10 to 11+ GPM for whole-home demand; electrics top out lower and lean on amperage. Match the fuel to your panel and your gas line.
• Condensing efficiency (UEF) — Condensing gas units at 0.95–0.98 UEF recover exhaust heat and cut fuel bills, worth the premium in cold climates.
• Venting requirements — Condensing units use cheap PVC; non-condensing need stainless venting. Electrics need none, which simplifies retrofits.
• Install cost — Electric whole-home units often need a 200-amp panel upgrade; gas units may need a larger gas line and a condensate drain. Budget the install, not just the box.
• Warranty — Look for 12 to 15 years on the heat exchanger; stainless exchangers can last 25 years.
• Hard-water maintenance — Plan on annual descaling in hard-water areas to protect flow and lifespan.

What matters less than marketing implies: flashy app dashboards and small UEF differences of a few hundredths rarely change real-world bills or comfort. Correct sizing, clean venting, and routine descaling determine whether you love or hate your unit far more than the smart features on the spec sheet.

FAQ

How many GPM do I need for a whole house? A typical family running two showers or a shower plus the kitchen wants 6 to 9 GPM, and homes with multiple simultaneous bathrooms should target 10 to 11+ GPM. Always size for your coldest incoming water, since the bigger temperature rise lowers usable flow.

Is gas or electric tankless better? Gas units deliver higher flow for whole-home use and work in cold climates, but need venting and a gas line. Electric units are cheaper to buy and install with no venting, but cap out at lower flow and may require a 200-amp panel upgrade.

What does condensing mean and is it worth it? A condensing unit captures heat from exhaust gases that a standard unit wastes, pushing efficiency to 0.95–0.98 UEF. It costs more up front but vents through inexpensive PVC and pays back in fuel savings, especially in cold regions.

How long do tankless water heaters last? With annual descaling, quality gas units like the Rinnai RX199iN run 18 to 20 years, and stainless heat exchangers such as Navien's are rated up to 25 years — well beyond the 10 to 12 years of a typical tank.

Do I really need to descale it every year? In hard-water areas, yes. Scale buildup chokes flow and shortens heat-exchanger life. A yearly vinegar or descaler flush takes under an hour and is the single biggest factor in long-term reliability.

Can a point-of-use unit replace my whole-home heater? No. Units like the EcoSmart ECO 11 and Bosch Tronic 3000 serve one or two fixtures. Use them to add fast hot water to a remote sink or bathroom, not to supply the whole house.

Bottom Line

For gas homes that want the best blend of flow, efficiency, and longevity, the Rinnai RX199iN Sensei at $1,700 is our Best Overall — 11.1 GPM, 0.98 UEF, and a near-20-year service life. If you are on electric or want to skip gas entirely, the EcoSmart ECO 27 at $580 is the Best Value, delivering whole-home hot water for warm-climate households with no venting and a lifetime element warranty. Run your fuel type, household flow needs, and budget through the decision tree above to land on the right pick from the full top ten.

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Sources

• This Old House — The 5 Best Tankless Water Heaters (2026)
• Bob Vila — Best Tankless Water Heaters
• Consumer Reports — Tankless Water Heater Ratings &amp; Buying Guide
• Popular Mechanics — Best Tankless Water Heaters
• Forbes Home — Best Tankless Water Heaters
• Rinnai — RX199iN Sensei spec sheet
• Navien — NPE-240A2 ultra-high-efficiency condensing water heater
• Rheem — RTEX-36 electric tankless spec sheet
• EcoSmart — ECO 27 and ECO 11 product pages
• Stiebel Eltron — Tempra 36 Plus electric tankless

*Tankless water heater review — tankless water heater reviews, rating, best tankless water heater 2027, and a review of the top gas and electric picks for homeowners.*

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