How are these tankless water heaters ranked?

They are ranked by a transparent Value Score computed from independently-measurable specs normalized to price. The full formula is published on the page — no black box — and the sliders let you reweight the factors that matter to you, which recomputes the ranking live.

How many tankless water heaters are compared and where does the data come from?

12 tankless water heaters are compared. Specs are sourced from standards-body listings and manufacturer spec sheets, with approximate street prices from major retailers; each unit lists its sources.

The page breaks down what genuinely differentiates these tankless water heaters and how each spec feeds the Value Score, so you can see why a unit ranks where it does rather than taking a verdict on faith.

Which brands of tankless water heater are included?

Brands compared include EcoSmart, Navien, Noritz, Rheem, Rinnai, Stiebel and Takagi.

How Much Does a Tankless Water Heater Cost? Unit + Running Cost

Rank by your priorities

Ranked for total cost of ownership — the preset below sorts by lowest running cost so the cheapest unit to own, not just buy, floats to the top. Every slider is yours to override.

For this specific use case — unique to this page

The real cost of a tankless: unit, install, and 15 years of running it

Unit price by fuel is the first fork, and it's wide. Electric whole-house tankless units are the cheapest to buy ($200\u2013$700) because there's no burner, heat exchanger metallurgy, or venting hardware. Gas non-condensing units land around $700\u2013$1,100; gas condensing \u2014 the most efficient, with cheap PVC venting \u2014 run $1,000\u2013$1,650+. But a cheap sticker can be the most expensive choice over time: an electric unit that saves you $500 up front can cost that back in a single panel upgrade or in higher electric-vs-gas running cost, depending on your utility rates.

Annual running cost is where tankless earns its keep \u2014 or doesn't. A typical U.S. household spends roughly $200\u2013$350/yr heating water with a gas tankless and $300\u2013$550/yr with electric resistance (heat-pump tanks beat both, but that's a different product). The swing is driven by two numbers: UEF (0.81 for a basic gas unit vs ~0.99 for electric vs ~0.96 for gas condensing) and your local price per therm / kWh. Because there's no standby loss \u2014 no tank of water kept hot 24/7 \u2014 tankless typically cuts 8\u201334% off a tank heater's water-heating energy.

Lifetime cost is the honest comparison, and it's where tankless usually wins. A tank heater costs less up front ($400\u2013$900) but lasts 8\u201312 years; a tankless costs more installed but lasts 15\u201320 years \u2014 roughly double \u2014 so you skip one full replacement cycle. Add the lower running cost, and over a 15-year horizon a well-matched tankless often reaches cost parity or better despite the higher install. The catch: hard water. Skip the annual descaling flush and scale shortens heat-exchanger life, flipping the lifetime math against you \u2014 budget $100\u2013$200/yr (or DIY).

Don't forget the rebates. High-efficiency gas condensing and ENERGY STAR units frequently qualify for federal tax credits (the 25C energy-efficient home improvement credit covers a percentage of qualifying water heaters, capped annually) plus utility and state rebates that can knock $100\u2013$600+ off the real cost. Always check your gas/electric utility's rebate portal and the current federal credit before you buy; it can make a condensing unit cheaper than a basic one after incentives.

Costing out a tankless — the full picture

Compare TOTAL cost of ownership, not sticker: unit + install + 15yr running cost + descaling
Gas condensing costs most up front but vents in cheap PVC and runs efficiently \u2014 often cheapest to own
Electric whole-house is cheapest to buy but may force a panel upgrade and higher running cost
Budget $100\u2013$200/yr for descaling if you have hard water \u2014 skipping it voids the lifetime savings
Check federal 25C tax credit + utility rebates BEFORE buying \u2014 can cut $100\u2013$600 off a high-efficiency unit

Reading guide — teaches you to drive the tool above

What a tankless water heater really costs — to buy and to run

The question "how much does a tankless cost" has two answers, and most buyers only ask the first. The purchase price splits hard by fuel: a quality gas tankless runs $700–$1,650 (condensing models at the top of that range), while electric whole-house units are far cheaper to buy at $200–$700 — but that sticker gap is misleading, because electric's cost shows up later on your power bill and in the panel upgrade an electric whole-house unit often demands. The second answer — the one that actually decides the cheapest unit to own — is running cost, and that's driven by UEF (efficiency) and your local fuel price. The tool below is pre-weighted toward low running cost so the cheapest-to-own unit rises to the top; every slider is yours.

→ Cold-climate or big household? Tap "cold climate" or "big family" above. Watching gas bills? Tap "lowest running cost." The tool re-ranks instantly.

What about installation cost?

Sticker price is only half the story — condensing units need special venting, electric units may need a panel upgrade. The tool ranks on unit value; use the fuel filter to compare within an install type (all-gas vs all-electric) so you're not comparing a cheap electric against a gas unit that costs $1,500 to vent. (A dedicated installation-cost calculator — the highest-demand tankless search — is live.)

Condensing vs non-condensing: the choice that drives both your bill and your install

This is the first real fork. A non-condensing unit (e.g. the Rinnai V75iN, ~0.81 UEF) is cheaper up front (~$780) but vents hot exhaust through expensive stainless-steel or Category III venting and wastes more heat. A condensing unit (Navien NPE, Rinnai RX, Rheem Prestige — 0.93–0.98 UEF) captures a second pass of heat from the exhaust, running cool enough to vent through cheap PVC and cutting gas use meaningfully. Rule of thumb: condensing costs $300–600 more for the unit but is usually cheaper to vent and pays back the difference in gas savings within a few years — especially if you run a lot of hot water. The tool's UEF axis is where this shows up; sort by it to see the efficiency spread directly.

Gas vs electric tankless: which one fits your house

The honest limiter on electric tankless isn't efficiency — electric units hit ~0.99 UEF — it's flow in cold climates and your electrical panel. The best electric units here (Stiebel Eltron Tempra 29, Rheem RTEX-27) top out around 2.9–3.1 GPM at a 70° rise and can demand 100+ amps of dedicated service, often forcing a panel upgrade. That's fine for a warm climate, a point-of-use application, or a small household — and electric wins on up-front price ($430–850) and needs no venting at all. Gas (natural gas or propane) is what a cold-climate whole-house family wants: 4.5–5.7 GPM at rise, no panel upgrade, but it needs a gas line and venting. Use the fuel filter above to compare like-for-like instead of pricing a $430 electric against a $1,500 gas unit that solves a different problem.

Why we don't just name a winner

"Best tankless" depends entirely on your fuel, climate and household size. A cold-climate family cares about flow; a bill-watcher cares about UEF; a landlord cares about warranty. One name buries that — the Value Score keeps it in your hands, formula in the open right above. (Sizing for a specific household? See our tankless sizing for a family of 4 walkthrough.)

The specs, briefly

UEF = efficiency, how much energy reaches the water (higher = lower bills). Flow @ 70° rise = real cold-weather simultaneous-shower capacity. HX warranty = years on the heat exchanger, the part that fails. Recirculation = instant hot water at the tap (built-in pump only — "recirc-capable" without a factory pump doesn't count here). Min-flow = how little flow fires it (low = no cold-water sandwich).

Specs verified Aug 2026 against manufacturer spec sheets + ENERGY STAR product finder. Prices are approximate street prices (unit only, not installed) pending live-retailer verification. Some links may be affiliate; that never changes the Value Score — the math runs on published specs, not payouts.

How much does a tankless water heater cost?

Rank by your priorities