Best overall A.O. Smith ProLine XE ATI-540H-N —
Highest overall score (95/100) — the strongest balance of specs, value and recency in this group.
Check price at amazon.com →Independent · sourced · Updated July 2026
Best Tankless Water Heaters (2026)
The best overall tankless water heater is A.O. Smith ProLine XE ATI-540H-N. The best value tankless water heater is EcoSmart ECO 24 ($525). The cheapest is Rheem RTEX-18 at $523.99. 9 tankless water heaters compared from $523.99 to $3583.27 across 8 brands — every figure sourced, updated July 2026.
9 tankless water heaters compared on the specs that matter and US price — ranked cheapest-first. Every spec and price links to its source and the date we captured it.
Our data Our pay-blind pick across the 8 tankless water heaters we ranked is A.O. Smith ProLine XE ATI-540H-N — the Platinum-tier leader on specs-per-dollar, never price or placement. The smart-money alternative is EcoSmart ECO 24 ($525). Category Champions, as of July 2026.
Which tankless water heater should you buy?
Three buyer-intent picks from the algorithmic ranking below — no paid placement.
As an Amazon Associate we earn from qualifying purchases. Prices verified 2026-07-11; live price may differ.
Key takeaways
- Lowest price: Rheem RTEX-18 at $523.99 (US retail price $523.99 listed verbatim on FactoryPure product page (SKU RTEX-18, "$ 523.99", data-price-raw="52399"), accessed 2026-07-11. Rheem.com publishes no MSRP for this model.).
- Typical price: from $523.99, median $1295.62, up to $3583.27 — across 7 priced.
- Tracked: 9 products across 8 brands, current through 2026-07-11.
- Compared on: Fuel type, Max flow rate gpm, Max btu per hour, Power input (kW), Uniform energy factor, Condensing type.
Best by the numbers
Objective winners — each is the leader on one measured spec, with the figure. No subjective ranking.
- Lowest price: Rheem RTEX-18 ($523.99)
- Highest maxBtuPerHour: Navien NPE-240A2 (199900 maxBtuPerHour)
- Highest powerInputKw: Stiebel Eltron Tempra 36 Plus (36 powerInputKw)
- Highest heatExchangerWarrantyYrs: Rinnai RU199iN (15 heatExchangerWarrantyYrs)
- Lowest weightLbs: EcoSmart ECO 24 (14.25 weightLbs)
Top 3 by quality
An algorithmic overall ranking from the data on this page — value for money, spec strength, and recency. 100% data-driven, no paid placement.
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A.O. Smith ProLine XE ATI-540H-N Quality score 95/100 Most powerful -
EcoSmart ECO 24 Quality score 84/100 Best value -
Rinnai RU199iN Quality score 73/100 Most powerful
How we rank: Value 45% · Spec strength 35% · Recency 20%. Scores are computed only within this category from published specs and prices — never influenced by commissions or placement. Method & open data →
What to look for
How to read the comparison — what each key spec means and the range across these tankless water heaters.
- Max btu per hour — higher is better (this group: 157000 to 199900).
- Power input (kW) — higher is better (this group: 18 to 36).
Comparison
| Compare | # | Tankless Water Heater | Price | Fuel type | Max flow rate gpm | Max btu per hour | Power input (kW) | Uniform energy factor | Condensing type | Source |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 |  Rheem RTEX-18 | $523.99 | electric | 4.4 | — | 18 | 0.94 | electric | rheem.com | |
| 2 | EcoSmart ECO 24 | $525 | electric | — | — | 24 | — | electric | ecosmartus.com | |
| 3 |  Stiebel Eltron Tempra 36 Plus | $1132 | electric | 8.2 | — | 36 | — | electric | stiebel-eltron-usa.com | |
| 4 |  Noritz NRC711-DV-NG | $1295.62 | natural-gas | 7.1 | 157000 | — | 0.89 | condensing | noritz.com | |
| 5 |  Rheem RTGH-95DVLN | $1499 | natural-gas | 9.5 | 199900 | — | 0.93 | condensing | files.rheem.com | |
| 6 |  Navien NPE-240A2 | $2099 | natural-gas | 11.2 | 199900 | — | 0.95 | condensing | navieninc.com | |
| 7 |  Bosch Greentherm T9900i SE 199 | $3583.27 | natural-gas | 11.2 | 199000 | — | — | condensing | bosch-homecomfort.com | |
| 8 | A.O. Smith ProLine XE ATI-540H-N | — | natural-gas | 10 | 199000 | — | 0.93 | condensing | hotwater.com | |
| 9 | Rinnai RU199iN | — | natural-gas | 11 | 199000 | — | 0.95 | condensing | rinnai.us |
Specs are as published by the manufacturer (or a reputable spec source where the official page was unavailable); prices are US launch MSRP. Full per-product records and all spec columns are in our open dataset.
Popular comparisons
Frequently asked questions
What is the cheapest tankless water heater?
Rheem RTEX-18 is the cheapest at $523.99 (US retail price $523.99 listed verbatim on FactoryPure product page (SKU RTEX-18, "$ 523.99", data-price-raw="52399"), accessed 2026-07-11. Rheem.com publishes no MSRP for this model.), as of 2026-07-11.
How much does tankless water heaters cost?
Across the 7 tankless water heaters with a published price, the median is $1295.62, ranging from $523.99 to $3583.27, as of 2026-07-11.
Which tankless water heater is best by the numbers?
Lowest price: Rheem RTEX-18 ($523.99). Highest maxBtuPerHour: Navien NPE-240A2 (199900 maxBtuPerHour). Highest powerInputKw: Stiebel Eltron Tempra 36 Plus (36 powerInputKw).
How many tankless water heaters are compared here?
9 tankless water heaters across 8 brands, with US price and key specs, current through 2026-07-11.
What is the best overall tankless water heater?
A.O. Smith ProLine XE ATI-540H-N — Highest overall score (95/100) — the strongest balance of specs, value and recency in this group.
What is the best value tankless water heater?
EcoSmart ECO 24 ($525) — Most specification per dollar of any tankless water heaters here at $525.
What is the most capable tankless water heater?
Rinnai RU199iN — Leads this group on the measured specs.
More hardware comparisons
How we compiled this
Covers whole-house and point-of-use on-demand (tankless) residential water heaters sold at a published US price, spanning natural-gas, propane, and electric units. Excludes conventional tank-style storage heaters, heat-pump (hybrid) tanks, and commercial rack/manifold systems. Price is typical US MSRP in USD. fuelType is an enum: natural-gas, propane, or electric (dual NG/LP units listed by their primary catalog listing). maxFlowRateGpm is the manufacturer maximum hot-water output in US gallons per minute; it is a peak figure at a nominal temperature rise, NOT a fixed-rise rating. maxBtuPerHour is rated gas input in BTU per hour; null for electric units. powerInputKw is rated electrical input in kilowatts; null for gas units. uniformEnergyFactor is the DOE Uniform Energy Factor (UEF), dimensionless, higher is better; null if not disclosed. condensingType is an enum: condensing, non-condensing, or electric. minActivationFlowGpm is the minimum flow in GPM required to fire the burner or heating element. ventType is an enum: pvc, stainless-steel, concentric, or none (ventless electric). maxTempF is the maximum output setpoint in degrees Fahrenheit. heatExchangerWarrantyYrs is the residential heat-exchanger warranty in years. wifiEnabled is a boolean: true only if native Wi-Fi/app control is built in, false if it requires an add-on module. weightLbs is unit dry weight in pounds.
Last verified 2026-07-11. We re-check published specs and prices on a recurring cadence and update this page when they change.
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