Flow-Rate Sizing, May 2026
11 GPM Tankless Water Heater Cost in 2026
11 GPM is the premium whole-house capacity tier. Installed cost runs $3,500 to $5,800 in 2026 for whole-house gas, with the unit and the gas-line resize accounting for most of the premium over a 7 GPM install.
Right-sizing test: can three people credibly take morning showers at the same time? If yes, you need 11 GPM, and in a cold-inlet winter even 11 GPM realistically covers two showers rather than three. If no, 7 to 9 GPM is the cost-effective choice. Buying capacity you do not use is paying for short-cycling that shortens heat-exchanger life.
What 11 GPM enables in daily use
The capacity headroom of an 11 GPM unit opens up combinations a 7 GPM unit cannot handle. Representative simultaneous-use scenarios:
- Three standard-flow showers running at once (7.5 GPM) plus a kitchen tap (2 GPM) plus a dishwasher (1 GPM): total 10.5 GPM
- A soaking-tub fill (6 to 8 GPM) plus a shower (2.5 GPM) without dip in either
- Two rain-head showers (3 GPM each) plus a washing machine fill (4 GPM): total 10 GPM
- Luxury master suite with body sprays (4 to 6 GPM by itself) plus second-bathroom shower
11 GPM is also the right tier for cold-climate homes where the 35F-rise spec rating gets eaten by the realistic 75F rise. Manufacturer flow tables show what happens: the Navien NPE-240A2 drops from 11.2 GPM at a 35F rise to 5.6 GPM at a 67F rise, and the Noritz EZ111DV from 11.1 GPM at a 30F rise to 4.9 GPM at an 80F rise (40F inlet water heated to 120F). Around 5 GPM is still enough for two simultaneous showers in winter, but not three.
The 11 GPM models that win on price-performance
Rinnai RU199iN, the flagship
Specifications below are from each manufacturer's own product page or spec sheet, checked October 2026. The Navien NPE-240A2 was listed at $2,199 at SupplyStop at the same check; other units vary widely by retailer, and contractor pricing varies again.
The Rinnai RU199iN is Rinnai's 11 GPM condensing unit. Rinnai lists 199,000 BTU maximum input, 11 GPM maximum flow and 0.95 UEF (its spec sheet gives 9.8 GPM at default settings and 11 GPM with parameter adjustment). Its product page does not publish flow at specific temperature rises; at the same input it sits close to the Navien and Noritz figures in the table further down. Its service network is the broadest of the four.
Navien NPE-240A2, the comfort-feature champion
The NPE-240A2 is rated at 199,900 BTU, 11.2 GPM at a 35F rise, 8.7 GPM at 45F and 5.6 GPM at 67F, with a 0.95 UEF (the pump-free NPE-240S2 is 0.96), per Navien's NPE-2 spec sheet. The "A2" adds the ComfortFlow recirculation pump and buffer tank as standard. It was listed at $2,199 at SupplyStop in October 2026. It is the strongest value at this tier if you want recirculation, because a separate pump is otherwise an add-on.
Noritz EZ111-DV-NG, the retrofit specialist
The EZ111DV is rated at 12,800 to 199,900 BTU and 0.98 UEF, and Noritz publishes a full flow table: 11.1 GPM at a 30F rise, 8.7 at 45F, 6.5 at 60F, 5.6 at 70F and 4.9 at 80F. It vents through 2, 3 or 4 inch PVC/CPVC, polypropylene, or an outdoor vent cap, and the EZ series is built to fit where an old tank stood, which keeps retrofit pipework short.
Rheem RTGH-95DVLN, the budget premium pick
The RTGH-95DVLN-3 is Rheem's largest condensing model: 199,900 BTU and 0.93 UEF, indoor, with an RTGH-X conversion kit for outdoor mounting. Rheem rates it at 9.5 GPM at a 35F rise, 8.5 GPM at 45F and 5.7 GPM at 67F. The lower 35F headline reflects its 9.5 GPM maximum-flow cap; at winter rises its flow matches the other 199,000 BTU units, because flow at a given rise is set by burner input and efficiency.
Itemised installed cost for a Rinnai RU199iN
4-bath suburban home, swap from a 75-gallon gas tank, fresh concentric vent, gas-line upgrade required:
| Line item | Cost | Notes |
|---|---|---|
| RU199iN-class unit | $1,500 to $2,200 | Estimate; NPE-240A2 listed at $2,199 at SupplyStop, Oct 2026 |
| Gas line resize, 1/2 to 3/4 inch, 30 ft run | $500 to $1,100 | Black iron or CSST, longer run than 7 GPM install |
| Gas meter upgrade (if needed) | $0 to $400 | Often a free utility upgrade but takes weeks |
| Condensing vent kit (PVC/CPVC or PP), 25 ft | $320 to $480 | Larger diameter than 7 GPM kit |
| Condensate neutraliser | $60 to $120 | Required by code |
| 120V electrical for controls | $100 to $300 | Often a new dedicated outlet |
| Isolation valves and flush ports | $80 to $160 | Required by warranty |
| Labour, 8 to 12 hours | $800 to $1,560 | Longer than 7 GPM install |
| Permit and inspection | $100 to $300 | Higher than smaller installs in some jurisdictions |
| Old water heater removal (75 gal) | $100 to $200 | Larger tank than typical |
| Total installed | $3,560 to $6,820 | 2026 4-bath conversion scenario |
The top of this table stacks every worst case at once (long gas run, meter swap, high labour), which is why it runs above the typical $3,500 to $5,800 range. The 7 GPM to 11 GPM premium is around $800 to $1,200 on our model, driven by the larger unit, the longer gas-line upgrade ($200 to $400 more) and the larger vent kit ($100 to $150 more).
The gas-line constraint that catches people out
An 11 GPM tankless at full fire draws 199,000 to 199,900 BTU per hour, roughly 199 cubic feet of natural gas an hour. The pipe-sizing tables in the fuel gas code (NFPA 54 / IFGC Table 402.4 series) cap how much gas a 1/2 inch line can deliver, and the cap falls with every foot of run, so a line sized for an old tank heater is usually too small. The result is either an upgrade to 3/4 inch line, or the unit is starved at full fire and you never see its rated GPM.
This is the single biggest unexpected cost on an 11 GPM install. A 30-ft gas-line run upgrade from 1/2 inch to 3/4 inch black iron costs $500 to $1,100. If your home is on CSST (corrugated stainless steel tubing), the upgrade is closer to $700 to $1,400 because of the labour required to chase the new line. The honest 11 GPM quote includes this line item even if the gas line is "fine for the existing tank"; it is not fine for the tankless.
Some 11 GPM installs also need the gas utility to swap the meter. Every meter has a rated capacity in cubic feet per hour; add the heater's roughly 199 CFH to the furnace, range and dryer, and an older meter can come up short. Your plumber totals the connected load, and the utility schedules the swap if it is needed.
How the rating changes with climate
The 11 GPM headline is a low-rise rating. What a 199,000 BTU unit actually delivers depends on how far it has to lift the incoming water. Published manufacturer figures, with the inlet temperature each rise implies at a 120F setpoint:
| Rise (inlet at 120F output) | Noritz EZ111DV | Navien NPE-240A2 | Rheem RTGH-95 |
|---|---|---|---|
| 45F (75F inlet) | 8.7 GPM | 8.7 GPM | 8.5 GPM |
| 60F (60F inlet) | 6.5 GPM | n/p | n/p |
| 67F to 70F (50F to 53F inlet) | 5.6 GPM (70F) | 5.6 GPM (67F) | 5.7 GPM (67F) |
| 80F (40F inlet) | 4.9 GPM | n/p | n/p |
| 90F (30F inlet) | 4.4 GPM | n/p | n/p |
n/p: not published by the manufacturer. Sources: Noritz EZ series spec sheet, Navien NPE-2 spec sheet, Rheem RTGH series brochure, all checked October 2026. The three agree because flow at a given rise is set by burner input: 199,000 BTU at about 95% thermal efficiency, divided by 500 times the rise, gives the same numbers to within a few tenths. To read the table for showers: a 2.5 GPM shower at about 105F draws roughly 2 GPM of 120F water when the inlet is 40F (the rest is cold), so about 5 GPM covers two winter showers, not three. Northern homes with three-shower mornings need either a second unit or a staggered schedule, and no single 199,000 BTU heater changes that.
Federal tax credit: ended for 2026 installs
The IRS Section 25C credit (30% of installed cost, capped at $600 per tax year for tankless) ended for any unit placed in service after December 31, 2025, under the One Big Beautiful Bill Act. A 2026 install gets no federal credit. If your unit was installed during 2025, you can still claim it on your 2025 return via IRS Form 5695.
State rebates worth stacking
Same stack as smaller-capacity installs:
- SoCalGas: tiered rebates of $80 to $1,300 by UEF on qualifying ENERGY STAR tankless units replacing a storage water heater, per the 2026 program schedule
- Energy Trust of Oregon: up to $400 for an ENERGY STAR gas tankless replacing a gas storage tank in NW Natural, Cascade Natural Gas, or Avista territory ($200 for UEF 0.82 to 0.95, $400 for UEF 0.96 and up)
- NYSERDA, Mass Save, and CenterPoint Energy MN have run tankless incentives in past program years; check dsireusa.org and your utility's own qualifying-product list for current amounts
Total cost of ownership over 20 years
Navien's NPE-2 spec sheet puts the NPE-240A2's annual gas use at 179 therms under the DOE test procedure, about $195 a year at the $1.09 per therm national average it assumes. Your own figure scales with your gas price and how much hot water the household actually draws. Over 20 years, add the installed cost, 20 years of gas at your rate, and annual descaling if your water is hard; a reader can run that sum with their own utility bill in a couple of minutes, and it beats any national average we could quote.
Bottom line
11 GPM is the right capacity for 4-bath houses, multi-generational households, and any home with a soaking tub or luxury shower fixtures. In cold climates it is also the realistic choice for 3-bath houses needing two simultaneous showers. Installed cost runs $3,500 to $5,800 in 2026. The Rinnai RU199iN dominates the premium segment; the Navien NPE-240A2 is the strongest value-with-recirculation choice; the Noritz EZ111-DV-NG wins on retrofits.
Related sizing and cost pages
Frequently asked questions
How much does an 11 GPM tankless cost installed in 2026?
An 11 GPM tankless installs at $3,500 to $5,800 in 2026 on our cost model. The Navien NPE-240A2 was listed at $2,199 at SupplyStop in October 2026; other units vary widely by retailer. The installation premium over a 7 GPM unit is around $800 to $1,200 on our model because the larger gas-line BTU load often forces a 3/4 inch supply that may need extending back to the gas meter. Most 4-bath or larger US homes need this capacity tier.
What does 11 GPM actually cover?
11 GPM supports three simultaneous standard-flow showers (2.5 GPM each = 7.5 GPM) plus a 2 GPM kitchen tap and a 1 GPM dishwasher with headroom. Or two showers plus a soaking-tub fill (6 to 8 GPM). It is the right tier for 4-bath houses, multi-generational households, or homes with luxury fixtures (rain heads, body sprays, soaking tubs).
Do I need an 11 GPM unit in a 3-bath house?
Usually no, unless the 3-bath house has unusual demand: a soaking tub on one of the bathrooms (which alone consumes 6 to 8 GPM during fill), or you live in a cold climate, where a unit's flow at a winter rise of 75F is roughly half its 35F-rise rating. In warm climates and standard-flow fixtures, a 9 GPM-rated unit is the cost-effective sweet spot for 3 baths.
Does the gas line need upgrading for an 11 GPM unit?
Usually. The 11 GPM units here are rated at 199,000 to 199,900 BTU per hour at full fire, which is roughly 199 cubic feet of natural gas per hour at about 1,000 BTU per cubic foot. The pipe-sizing tables in the fuel gas code (IFGC Table 402.4 series) cap how much a 1/2 inch line can carry, and the allowance falls as the run gets longer, so most whole-house units need 3/4 inch or larger pipe from the meter. Noritz's EZ111DV is the main exception: its spec sheet allows a 1/2 inch line up to 40 ft. If the meter's rated capacity is below the combined load of every gas appliance in the house, the gas utility has to swap it, which adds scheduling time.
Is the cost premium over 7 GPM worth it?
Only if the demand profile justifies it. Buying an 11 GPM unit for a 2-bath house means paying $800 to $1,200 extra for capacity you will never use. The unit will short-cycle on low-demand draws, which shortens heat-exchanger life. Right-size based on your worst-case simultaneous demand, not your aspirational future home.