Best Natural Gas Tankless Water Heater

A large storage tank can empty at the worst possible moment. One person takes a long shower, another fills the washing machine, and the kitchen faucet begins to run. The last person gets a stream that fades from warm to icy. A natural gas tankless water heater removes the fixed tank limit by heating water as it passes through the unit.

The Rinnai RXP199iN is the best natural gas tankless water heater for most large homes. It pairs an 11.1-GPM maximum rating with a 199,000-BTU burner, a built-in recirculation pump, Wi-Fi control, and a 0.98 UEF rating. The Navien NPE-240A2 is a close rival for buyers who want an internal pump and buffer tank, while the Noritz EZ111DV Pro is a fine pick for replacing a large storage heater.

Best Natural Gas Tankless Water Heaters at a Glance

Best Overall: Rinnai RXP199iN

The Rinnai RXP199iN takes the top spot because it joins high heating output, low fuel waste, and an internal recirculation pump inside one wall-mounted cabinet. Its burner can rise to 199,000 BTU when several fixtures open. It can also reduce its fire for a light faucet draw.

That wide burner range helps the unit respond to changing household demand. Washing hands does not need the same heat as two showers and a dishwasher. The heater adjusts its gas use rather than firing at full power for every task.

The internal pump is one of the main reasons to buy the RXP model. A recirculation system moves warm water through a return pipe or an approved crossover setup. This can shorten the wait at a distant bathroom and cut the amount of cold water sent down the drain.

Rinnai gives the heater an 11.1-GPM maximum rating. That number comes from mild inlet conditions. Cold winter water lowers the flow that the burner can heat to the chosen outlet setting.

The RXP199iN carries a 0.98 UEF rating. A condensing heat exchanger pulls more warmth from the exhaust before the gases leave the home. The cooler exhaust creates liquid condensate, so the heater needs a drain.

The unit can mount indoors or outdoors with the proper setup. Outdoor placement can free wall room inside the house and remove a long indoor vent run. Cold-region owners still need proper freeze protection for the unit and nearby pipes.

Wi-Fi support gives the owner phone access to temperature settings and operating information. Pump schedules can also help reduce needless recirculation during hours when nobody uses hot water.

Best match: A three- or four-bathroom home, a large family, or a house with long pipe runs.

Best for Recirculation Comfort: Navien NPE-240A2

The Navien NPE-240A2 is built for households that dislike long faucet waits and brief cold bursts. Its ComfortFlow system combines an internal recirculation pump with a small buffer tank and matched controls.

The buffer tank holds a small amount of warm water inside the cabinet. It can soften the temperature dip that may occur when one short water draw ends and another begins soon afterward.

Navien publishes flow rates at several temperature rises. The NPE-240A2 reaches 11.2 GPM at a 35°F rise, 8.7 GPM at a 45°F rise, and 5.6 GPM at a 67°F rise.

These numbers show why winter sizing matters. Water entering at 50°F and leaving at 120°F needs about a 70°F rise. Under that load, the heater will perform closer to its 67°F-rise rating than its 35°F-rise rating.

A 5.6-GPM flow can feed two 2.0-GPM showers with room left for a light faucet. A third shower may push the heater beyond its comfortable limit when incoming water is very cold.

The internal pump can work with a dedicated return line. It may also work with a compatible crossover valve in a house that lacks a return pipe. An on-demand button can start the pump before a shower, which avoids running it all day.

The NPE-240A2 is a condensing model and needs a drain for the water created inside the exhaust path. Indoor and outdoor mounting are supported under the listed installation rules.

Best match: A family that wants shorter waits, stable shower temperature, and a factory-installed pump.

Best Smart Pick: Rheem IKONIC RTGH-SR11i

The Rheem IKONIC RTGH-SR11i pairs a 199,900-BTU burner with an internal recirculation pump and built-in Wi-Fi. Its 11.2-GPM maximum rating puts it among the strongest single residential units.

Rheem’s EcoNet connection lets the owner set water temperature, watch usage, receive service alerts, and set recirculation schedules from a phone. This can help when the heater sits in a basement, garage, attic room, or exterior cabinet.

The internal pump can keep warm water closer to distant fixtures. A schedule can run the pump before the household wakes and again before the evening shower period. It can stay off during the middle of the night.

Hot Start programming keeps the heater ready between closely spaced water draws. This can reduce the brief cool patch that sometimes appears when a shower pauses and restarts.

The RTGH-SR11i has a 0.96 UEF rating. Its stainless steel heat exchangers are made to face repeated heating cycles and condensation.

Rheem permits flexible installation choices with approved vent parts. Some setups may work with a half-inch gas line, but pipe length, pressure, elbows, and the demand from other appliances still control the final answer.

Never assume that an existing half-inch line can feed a 199,900-BTU burner. A contractor must calculate the full gas load before installation.

Best match: A large connected home that wants phone control, pump scheduling, and strong cold-weather flow.

Best Storage-Tank Replacement: Noritz EZ111DV Pro

The Noritz EZ111DV Pro is made with storage-tank replacement work in mind. Its water connections sit at the top, which can reduce pipe changes when an old tank is removed.

The 2026 Pro version reaches 11.1 GPM and has a 199,900-BTU maximum input. Its 0.98 UEF rating places it beside the most fuel-efficient residential gas units.

A built-in front panel gives the owner direct access to temperature and operating information. Bluetooth access can help with setup and service work.

Natural gas is the standard fuel setup. The package also includes parts for an approved conversion to propane. Buyers using natural gas can leave the unit in its factory fuel setup.

The long heat-exchanger warranty is another reason to consider Noritz. Coverage changes when a recirculation system is added, so read the written terms before connecting a pump.

The EZ111DV Pro is a good fit when the old heater has top water pipes and a suitable wall behind it. Noritz also sells tank-replacement packages with valves and vent parts for selected jobs.

Best match: A homeowner replacing a 50- or 75-gallon gas tank who wants to reduce pipe changes.

Best Without an Internal Pump: Rinnai RX199iN

The Rinnai RX199iN shares much of the RXP model’s heating hardware. It reaches 11.1 GPM, uses a 199,000-BTU maximum burner, and carries a 0.98 UEF rating.

The main difference is the lack of an internal recirculation pump. This can save money when the house has short pipe runs or already uses an external pump.

A compact home may not need recirculation. The kitchen and bathrooms may sit close enough to the heater for hot water to arrive quickly on its own.

The RX199iN is recirculation-ready, so an approved pump can be added later. This gives the owner room to test the normal wait time before paying for more parts.

The unit also supports natural gas and indoor or outdoor placement under the proper setup. Wi-Fi access is included.

Best match: A large home that needs high heating output but does not need a factory-installed pump.

Check the Rinnai RX199iN on Amazon.

Best for a Medium Home: Rinnai RX180iN

The Rinnai RX180iN lowers the maximum burner input to 180,000 BTU and the headline flow to 10.0 GPM. It keeps the 0.98 UEF rating found on the larger RX199iN.

This model may suit a two- or three-bathroom home where two showers sometimes run together but heavy whole-house demand is rare.

A smaller heater can cost less to buy. Installation labor may remain close to the cost of fitting a larger model, so the price gap should be weighed against future demand.

Do not reduce heater size merely to save a small amount. Check the winter inlet temperature and add the flow from every fixture that may run at once.

Best match: A medium house with moderate peak use and no internal pump need.

Check the Rinnai RX180iN on Amazon.

How Many GPM Does Your Home Need?

Start by adding the fixtures that may run at the same time. A modern shower may use 1.5 to 2.5 GPM. A bathroom faucet may use 0.5 to 1.5 GPM. A kitchen faucet may draw close to 2.0 GPM.

Two 2.0-GPM showers create 4.0 GPM of demand. Add a 1.5-GPM kitchen faucet and the total reaches 5.5 GPM.

The heater must deliver that flow at the needed temperature rise. A model with an 11.2-GPM headline rating may provide close to half that flow during a cold northern winter.

Use low-flow shower heads when household demand sits near the heater’s limit. Dropping each shower from 2.5 GPM to 1.8 GPM can free more capacity for a sink or dishwasher.

Why Temperature Rise Changes Flow

Temperature rise is the difference between incoming cold water and the chosen hot-water setting. Water entering at 50°F and leaving at 120°F needs a 70°F rise.

Water entering at 75°F only needs a 45°F rise to reach the same outlet setting. The burner can heat more gallons per minute because each gallon needs less added heat.

This is why the same natural gas tankless heater performs differently in Florida and Minnesota. The heater has the same burner. The colder home gives that burner a steeper hill to climb.

Do You Need a Recirculation Pump?

A tankless heater begins warming water quickly, but hot water still needs time to travel through the pipes. A distant bathroom may wait for a minute or longer.

A recirculation pump keeps warm water closer to the fixtures. It can use a dedicated return line or an approved crossover valve.

Constant pump operation can waste gas because warm pipes lose heat. Timed, sensor-based, or button-operated recirculation is usually the better choice.

Pipe insulation helps warm water remain hot while it travels around the loop. It can also reduce the number of burner cycles.

Will the Existing Gas Line Work?

A standard gas storage heater may use a 30,000- to 50,000-BTU burner. A large tankless model can approach 200,000 BTU.

The old fuel pipe may not carry that much gas. Pipe capacity depends on diameter, length, pressure, elbows, and the demand from every connected appliance.

A furnace, range, fireplace, dryer, and water heater may all run on the same cold evening. The contractor must calculate the combined load.

A weak gas supply can cause ignition faults, low outlet temperature, or trouble with nearby appliances.

Condensing or Non-Condensing?

A condensing heater uses a second heat exchanger to pull more warmth from the exhaust. This raises fuel efficiency and lowers exhaust temperature.

The cooler exhaust allows approved plastic vent pipe on many models. It also creates acidic condensate that needs a drain and may need a neutralizer.

A non-condensing heater usually costs less. Its exhaust is hotter and may need stainless steel vent pipe, which can raise the installed cost.

For most indoor whole-house jobs, a condensing heater gives the better long-term package. A non-condensing outdoor model may make sense when the climate permits exterior mounting.

Indoor or Outdoor Installation?

An indoor heater stays protected from rain, wind, and severe cold. It needs approved intake and exhaust pipes.

An outdoor heater removes the indoor vent run and frees wall room inside the house. It still needs electrical power, a gas line, water pipes, and proper clearance.

Exterior water pipes can freeze. Cold-region installations need insulation, approved heat protection, and careful pipe placement.

Outdoor placement also puts the unit closer to weather, insects, leaves, and airborne dirt. Routine checks become more valuable.

Installation Costs People Miss

The heater is only one part of the bill. A full job may need service valves, water-pipe changes, gas-line work, vent parts, wall backing, a condensate drain, an electrical outlet, permits, and old-tank removal.

A simple replacement may remain near the lower end of local labor costs. A full tank-to-tankless conversion can pass $2,000 after the heater and added work are counted.

A two-unit cascade for a very large home can cost far more. It may need shared controls, more gas capacity, added vent work, and a larger wall area.

Get one written installed price before ordering the heater. Some contractors do not fit equipment bought by the homeowner.

Maintenance and Hard Water

Minerals can collect inside the heat exchanger. Hard water leaves a chalky layer that slows heat transfer and narrows the water passages.

Many homes need periodic flushing with an approved descaling liquid. The service interval depends on water hardness and daily use.

Isolation valves make flushing easier. The inlet screen should also be checked for sand, rust, and pipe debris.

Keep exterior vents free from leaves, nests, snow, and dirt. A technician should inspect the burner, fan, seals, vent joints, and condensate path as listed in the owner manual.

Common Buying Mistakes

The most common mistake is choosing by maximum GPM alone. Flow at the home’s winter temperature rise tells a better story.

Another mistake is ignoring the gas pipe. A large burner may need a new line from the meter or regulator.

Some buyers forget the condensate drain and electrical outlet. A gas tankless heater still needs power for the fan, ignition, pump, and control board.

Others expect instant hot water at every faucet. A distant fixture still waits for water to move through the pipe unless the home uses recirculation.

Do not choose the largest unit without checking low-flow operation. A good heater should respond to a small faucet draw as well as a full morning load.

Which Natural Gas Tankless Water Heater Should You Buy?

Choose the Rinnai RXP199iN for the best mix of high flow, fuel efficiency, built-in recirculation, Wi-Fi control, and mounting flexibility.

Choose the Navien NPE-240A2 when short faucet waits, a buffer tank, and published cold-water flow rates matter most.

Choose the Rheem IKONIC RTGH-SR11i when phone control, pump scheduling, and strong flow sit at the top of your list.

Choose the Noritz EZ111DV Pro for a storage-tank replacement with top water connections and long heat-exchanger coverage.

Choose the Rinnai RX199iN when you need premium output without an internal pump. Pick the Rinnai RX180iN for a medium home with lighter peak demand.

The best natural gas tankless hot water heater should match winter inlet temperature, simultaneous fixture demand, fuel-pipe capacity, vent location, and recirculation needs. When those pieces line up, a small wall-mounted unit can feed long showers without a bulky storage tank waiting in the corner.