Tankless Gas, Installed
Tankless Gas Water Heater Installation Cost
A whole-house tankless gas water heater installed costs $2,500 to $5,000 in most US homes in 2026. The unit itself is $1,000 to $2,500. The install premium versus a tank swap is $1,500 to $2,500, driven by four required upgrades: gas-line upsize, dedicated vent, condensate drain, and a 120V outlet at the unit. Below, the realistic cost by configuration, condensing vs non-condensing decision, and the recirculation-pump option.
Quick answer: $2,100 to $3,400 for a non-condensing 7 to 8 GPM unit in a mild climate. $2,900 to $5,000 for the most-common condensing 9 to 11 GPM configuration. $1,800 to $3,300 for an outdoor mild-climate install that skips the vent run.
Cost Table
Tankless Gas Installation Cost by Configuration
Pricing reflects current Rinnai, Navien, Rheem, and Noritz model lines at major plumbing distributors. Install cost includes the four required upgrades detailed below.
| Type | Unit Cost | Install | Total Installed | Best For |
|---|---|---|---|---|
| Non-condensing 7 to 8 GPM | $900 to $1,400 | $1,200 to $2,000 | $2,100 to $3,400 | Mild climate, 2 to 3 bath, gas-line near unit |
| Non-condensing 9 to 11 GPM | $1,200 to $1,800 | $1,300 to $2,200 | $2,500 to $4,000 | Cold climate, 3 to 4 bath, family of 4 to 5 |
| Condensing 9 to 11 GPM (PVC vent) | $1,500 to $2,500 | $1,400 to $2,500 | $2,900 to $5,000 | Most common new-install configuration |
| Outdoor tankless gas | $1,000 to $1,800 | $800 to $1,500 | $1,800 to $3,300 | Mild climate, exterior wall placement, no vent run |
The Real Install Premium
The Four Upgrades a Tankless Gas Install Requires
A tank-to-tankless gas conversion is not a like-for-like swap. The existing gas line, vent, and electrical at the tank location were sized for a 40,000 BTU/hr atmospheric tank with no condensate. The tankless needs all of them upgraded. Quotes that omit one of these four items are either incomplete or assume the homeowner will discover the cost later.
| Upgrade | Cost | Reason |
|---|---|---|
| Gas line upsize (1/2 inch to 3/4 inch or 1 inch) | $300 to $1,000 | Tankless gas peaks at 180k to 199k BTU/hr versus 40k for a tank. Existing 1/2 inch line is undersized in nearly all cases. |
| New dedicated vent (PVC for condensing, stainless for non-condensing) | $300 to $800 | Tankless cannot reuse the tank's atmospheric B-vent. Sealed combustion requires a dedicated two-pipe direct vent system. |
| Condensate drain to floor drain or condensate pump | $100 to $400 | Condensing units produce 0.5 to 1 gallon of acidic condensate per hour at peak. Drain must be neutralised in some jurisdictions. |
| 120V electrical outlet at the unit | $100 to $300 | Tankless gas controls and the integral fan need 120V power. Tank atmospheric units need none. Add an outlet if not present. |
Sum of the four upgrades: $800 to $2,500. That is the structural reason why tankless gas installs cost $1,500 to $2,500 more than a tank swap. The math is honest. A contractor quoting $1,800 for a tankless install is either going to skip required work or hit you with change orders. Get the gas-line size, the vent material and run length, the condensate path, and the electrical work specified in writing on the quote.
Condensing Decision
Condensing or Non-Condensing? The Real Difference
Condensing tankless gas units have a second heat exchanger that extracts additional energy from exhaust gases by cooling them below the dew point of water vapor. The recovered latent heat lifts efficiency from the 80 to 84 percent UEF range (non-condensing) to 90 to 96 percent UEF (condensing). On a typical household's annual gas use, that is roughly $50 to $100 per year in operating savings. Over a 20-year unit lifespan, $1,000 to $2,000 in cumulative savings.
Three other practical differences matter. First, vent material and cost. Non-condensing exhaust runs at 300 to 400 degrees Fahrenheit and requires stainless steel or Category III vent material at $15 to $30 per linear foot. Condensing exhaust runs at 110 to 130 degrees Fahrenheit and uses Schedule 40 PVC at $3 to $6 per linear foot. On a 25-foot vent run, the material savings on PVC roughly offset the unit-cost premium of the condensing model. Second, condensate management. Condensing units produce 0.5 to 1 gallon of slightly acidic condensate per hour at peak operation. The condensate must drain to a floor drain or condensate pump, and some jurisdictions require a neutralisation cartridge ($30 to $80) before discharge. Third, lifespan parity. Both technologies last 15 to 20 years with annual flushing maintenance per manufacturer guidance.
The honest decision rule: condensing wins in nearly all new installations because the operating savings and cheaper venting offset the upfront premium. Non-condensing makes sense only when the existing vent path constraints favour stainless and the homeowner plans to sell the home within 5 years. The current ENERGY STAR criteria for gas water heaters effectively require condensing technology to qualify, and the federal Section 25C tax credit (up to $150 for tankless gas) is available only for ENERGY STAR-qualifying models.
Optional Add-On
The Recirculation Pump Decision
Tankless gas units have a small but real lag between when you open the tap and when hot water arrives. The cold-water sandwich is the volume of cold water sitting in the supply pipe between the heater and the fixture. For a fixture 30 feet from the heater through 3/4 inch pipe, that is roughly 0.6 gallons of cold water at the rate of 1.5 GPM, or about 24 seconds of waiting. For a tank water heater the cold sandwich is much smaller because the tank is already at temperature and the recovery is essentially instantaneous after the cold slug clears.
A recirculation pump and dedicated return line keep the supply pipe near hot temperature continuously. Hot water arrives at the tap within 2 to 3 seconds. Cost is $300 to $800 for the pump and $200 to $600 if a return line must be added. Some Navien and Rinnai models include the pump as a built-in feature; the no-return-line variants use the cold supply as the return path with a crossover valve at the farthest fixture, which works but slightly raises cold-water temperature briefly each cycle.
The honest evaluation: skip the recirculation pump on the first install if the budget is tight, and add it later if the cold-water-wait frustration becomes meaningful. The pump is a $300 to $800 retrofit at any time. Some households genuinely do not mind the wait; for them the recirculation pump is unnecessary energy use (the pump runs continuously or on a timer). For households that prioritise convenience the pump is a real quality-of-life upgrade.
Brand Landscape
Major Tankless Gas Brands and Where They Fit
Four brands dominate residential tankless gas in the US. Rinnai and Noritz are Japanese manufacturers with deep tankless heritage, dating to 1970s commercialisation in Japan where tankless is the residential default. Navien is a Korean manufacturer that grew US share aggressively in the 2010s with the NPE-A condensing line. Rheem produces tankless under its own brand and OEMs for several private labels. Each has a sweet spot.
Rinnai V-series (V53, V65, V75) are non-condensing units priced in the $700 to $1,200 range, suitable for mild-climate or warmer-incoming-water installs. The Sensei RU-series (RU130, RU160, RU180, RU199) are condensing units in the $1,400 to $2,200 range and represent the mainstream new-install choice. Navien NPE-A2 series are condensing units with built-in recirculation in the $1,800 to $2,500 range, often spec'd when recirculation is on the requirements list. Rheem RTGH-series are condensing units priced competitively at $1,200 to $1,700, sold through Home Depot and easy to source. Noritz NRC and NRCB lines compete across the same price points with strong professional installer support.
Warranty terms cluster around 12 years on the heat exchanger and 5 years on parts. Annual flushing maintenance is required to keep the warranty valid; skipping it for several years can void warranty coverage on the heat exchanger. For brand-detail comparison see the top brands page.
FAQ
Tankless Gas Installation Questions
How much does a tankless gas water heater cost installed?
A whole-house tankless gas water heater installed costs $2,500 to $5,000 in 2026. The unit itself runs $1,000 to $2,500 (Rinnai, Navien, Rheem, Noritz are the main brands). Install runs $1,500 to $2,500 because of three upgrades the existing tank install did not need: gas-line upsize, dedicated vent, and condensate drain (for condensing units).
What is the difference between condensing and non-condensing tankless gas?
Condensing units extract additional heat from exhaust gases (typically 90 to 96 percent UEF) by cooling the exhaust below the dew point and recovering latent heat. Non-condensing units run hotter exhaust (typically 80 to 84 percent UEF) and use stainless or PVC vent at higher temperatures. Condensing units cost $300 to $700 more upfront but save 10 to 15 percent on operating cost. They use cheaper PVC venting which offsets some of the unit-cost premium.
Why does tankless gas need a bigger gas line?
A standard 50 gallon tank water heater draws 40,000 BTU/hr at peak. A whole-house tankless gas unit draws 180,000 to 199,000 BTU/hr at peak, roughly four to five times the load. The existing 1/2 inch gas line that served the tank cannot deliver that much fuel, especially when the furnace or range is also firing. A 3/4 inch or 1 inch line is typically required, costing $300 to $1,000 to install depending on run length.
Is tankless gas worth the extra cost?
Usually yes if you keep the home 10+ years. Tankless gas costs $1,500 to $2,500 more than a tank install. It saves $100 to $200 per year on operating cost (efficiency 90 percent UEF vs 60 to 65 percent UEF for tank). Lifespan is 15 to 20 years vs 10 to 12 for tank, so over a full ownership cycle you avoid one tank replacement. Total ownership-cost advantage is $1,500 to $4,000 over 15 years, plus the never-runs-out hot water benefit.
Do I need a recirculation pump on a tankless gas heater?
Optional but increasingly standard. A recirculation pump and dedicated return line eliminate the cold-water sandwich (the brief delay before hot water arrives at the tap). Cost is $300 to $800 for the pump plus $200 to $600 if a return line must be added. Some Rinnai and Navien models have integrated pumps. If hot-water wait time is a frustration, the recirc system is worth the add. If not, skip it.
Compare
Related Cost Pages
Gas tank install
$1,400 to $3,200, simpler than tankless gas
Tank to tankless conversion
$3,500 to $6,500 with payback math
Tankless electric
$1,000 to $2,500 plus probable panel upgrade
Tank vs tankless
Side-by-side cost and lifespan comparison
Top brands
Rinnai, Navien, Rheem, Noritz models compared
Permits
IFGC, vent code, gas-line sizing requirements