Best Condensing Tankless Water Heaters: 15 Spec-Based Picks
As an Amazon Associate we earn from qualifying purchases. Links on this page are affiliate links.
Choosing the best condensing tankless water heaters requires comparing efficiency ratings, flow rates, and venting requirements. We analyzed 15 models based strictly on their published specifications. The Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater leads because its 0.98 UEF rating and 11.1 GPM capacity handle high-demand homes effectively. This guide helps you decide which unit fits your home’s hot water needs, fuel source, and installation space.
Quick picks
The best fit for you
- You need high capacity for large homes Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater Its 11.1 GPM flow rate handles simultaneous high demand.
- You want the most compact model on the list Rinnai Commercial 9 GPM Indoor Condensing Water Heater Its 11.5-inch width is the narrowest chassis available.
- You need outdoor propane heating for small homes Rinnai 9 GPM Outdoor Propane Condensing Heater It delivers 9 GPM of propane power outdoors.
- You want combined home heating and hot water Rinnai I-SERIES Plus Condensing Combi Boiler It functions as a boiler with 199K BTU capacity.
Our 15 picks
Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater
Best for: large homes needing high-capacity dual-fuel heating
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Propane or Natural Gas
- Flow Rate
- 11.1 GPM
- Installation Location
- Indoor/Outdoor
- Dimensions
- 30.1 x 18.5 x 30.1 inches
- Weight
- 55 pounds
View on Amazon: Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater
This condensing unit delivers up to 11.1 GPM across natural gas or propane setups. It features a 0.98 Uniform Energy Factor (UEF) and supports both indoor and outdoor placement. You can supply up to seven fixtures simultaneously from a single 55-pound cabinet. It suits large households that require high simultaneous hot water flow and the flexibility to switch between natural gas and propane.
Pros
- Delivers up to 11.1 GPM to run up to seven fixtures at once
- High energy efficiency factor of 0.98 UEF
- Operates on either natural gas or propane using Smart Sense control
- Indoor and outdoor mounting capability via Versa Vent
Cons
- Requires separate RX-OVC vent cap for outdoor installation
- Controlr WiFi module is not included
- Labor warranty drops from five years to one year without registration within 90 days
Good fit if
- You need high flow capacity to supply up to seven fixtures simultaneously.
- You want the versatility to run on either natural gas or propane.
- You plan to mount the unit indoors or outdoors.
Skip if
- You want built-in Wi-Fi out of the box without buying an add-on module.
- You do not want to register the unit within 90 days to keep the full labor warranty.
Verdict: Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater pairs a 0.98 UEF efficiency rating with an 11.1 GPM capacity for high-demand homes. Its dual-fuel capability and flexible mounting make it adaptable to diverse utility setups.
Ranein 5.1 GPM Condensing Natural Gas Water Heater
Best for: Low-elevation homes needing moderate hot water capacity
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 5.1 GPM
- BTU
- 120,000 BTU
- Voltage
- 120 V
- Temperature Control
- 95°F to 149°F, ±1°F
View on Amazon: Ranein 5.1 GPM Condensing Natural Gas Water Heater
The Ranein 5.1 GPM Condensing Natural Gas Water Heater supplies on-demand hot water using a 120,000 BTU modulating burner. Its condensing system recycles exhaust heat to preheat incoming water, letting you set temperatures from 95°F to 149°F. Measuring 22 by 14.2 by 6.4 inches, the unit includes an integrated 114W anti-freeze heater and 3/4-inch NPT fittings. It suits you if you need a compact indoor unit for two concurrent fixtures.
Pros
- 5.1 GPM flow rate powered by a 120,000 BTU 4-stage modulating burner
- Touchscreen control adjusts temperature from 95°F to 149°F at 1°F precision
- Built-in 114W anti-freeze protection activates below 42.8°F
- Installation kit includes Category III stainless steel vent pipe and condensate drain line
Cons
- Not recommended for elevations above 2,000 feet
- 5.1 GPM maximum flow provides lower capacity than larger whole-home models
Good fit if
- You need up to 5.1 GPM of hot water for one to two simultaneous fixtures
- You live in cold climates and require automated freeze defense down to 42.8°F
- You want a compact 22-inch wall-mounted unit that includes venting pipe hardware
Skip if
- You live at an elevation above 2,000 feet
- You need higher peak flow rates to run three or more showers at once
Verdict: Ranein 5.1 GPM Condensing Natural Gas Water Heater delivers reliable mid-range capacity and automated freeze protection in a compact wall-mount chassis. It provides balanced condensing efficiency for low-elevation homes with moderate simultaneous hot water needs.
VancEpic 5.1 GPM Propane Condensing Water Heater
Best for: propane-powered small homes and apartments
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Propane
- Flow Rate
- 5.1 GPM
- BTU
- 120,000 BTU/hr
- Installation Location
- Indoor
- Temperature Control
- 95°F to 149°F
View on Amazon: VancEpic 5.1 GPM Propane Condensing Water Heater
This indoor condensing tankless water heater runs on propane and delivers up to 5.1 GPM using a 120,000 BTU heat output. You get a stainless steel condensing heat exchanger that reclaims exhaust heat, plus an integrated 114W anti-freeze protection system. With temperature adjustments spanning 95°F to 149°F, it suits you if you run a smaller home or apartment needing steady hot water.
Pros
- Delivers up to 5.1 GPM with a 120,000 BTU output
- Durable stainless steel condensing heat exchanger captures exhaust energy
- Built-in 114W anti-freeze protection system for sub-zero conditions
- Comes with vent pipe and condensate drain line included
Cons
- Limited to a 2-year warranty on parts and heat exchanger
- Configured specifically for propane rather than natural gas
- Top flow rate of 5.1 GPM restricts simultaneous high-volume usage
Good fit if
- You heat with liquid propane and want an efficient condensing indoor unit.
- You live in an apartment or small home running one or two fixtures at once.
- You need built-in freezing protection for an indoor space subject to cold snaps.
Skip if
- You need a natural gas connection instead of propane.
- You have a large household requiring flow rates above 5.1 GPM.
- You want longer than a 2-year warranty on major components.
Verdict: VancEpic 5.1 GPM Propane Condensing Water Heater delivers efficient indoor heating with stainless steel components and built-in freeze defense. It provides a practical propane solution for smaller households that do not require high concurrent flow rates.
Rinnai I-SERIES Plus Condensing Combi Boiler
Best for: combined home heating and domestic hot water
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas or Propane
- BTU
- 175K BTU / DHW 199K BTU
- Installation Location
- Indoor
- Certification
- 96% AFUE
- Dimensions
- 45.3 x 19.5 x 19.5 inches
View on Amazon: Rinnai I-SERIES Plus Condensing Combi Boiler
The Rinnai I-SERIES Plus Condensing Combi Boiler handles both space heating and domestic hot water in a single indoor appliance. It delivers 175,000 BTU for home heating and 199,000 BTU for domestic hot water with a 96% AFUE rating. You get built-in Wi-Fi monitoring and support for natural gas or propane. It suits you if you need whole-home heating alongside on-demand hot water from one condensing system.
Pros
- Dual-purpose combi design supplies space heating and domestic hot water
- High operating efficiency with a 96% AFUE rating
- Smart Connect Wi-Fi capability and front panel digital display
- Common venting capability supports up to 8 units
Cons
- Large physical footprint measuring 45.3 inches tall and weighing 79.4 pounds
- Restricted to indoor installation locations
- Full 5-year labor warranty requires product registration within 90 days
Good fit if
- You need a single gas appliance for both domestic hot water and home heating.
- You want high-efficiency condensing operation with a 96% AFUE rating.
- You want built-in Wi-Fi connectivity for monitoring and control.
Skip if
- You only require dedicated domestic hot water without space heating.
- You need an outdoor-rated water heater.
- You have tight wall clearance unable to fit a 45.3-inch tall cabinet.
Verdict: Rinnai I-SERIES Plus Condensing Combi Boiler pairs home heating and domestic hot water into a single 96% AFUE condensing appliance. It is an ideal space-saving replacement for standalone boilers and separate water heaters.
Thermomate 5.28 GPM Indoor Natural Gas
Best for: one- to two-bath homes using natural gas
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 5.28 GPM
- BTU
- 114,000 BTU/hr
- Installation Location
- Indoor
- Voltage
- 120 V
The Thermomate 5.28 GPM Indoor Natural Gas is an indoor condensing water heater delivering up to 114,000 BTU/hr with a 0.86 UEF rating. Its dual heat exchanger combines stainless steel and copper to supply hot water between 90°F and 140°F. If you have a one- to two-bathroom home with a 1/2-inch gas line and 3-inch venting, this unit offers on-demand heating with built-in freeze protection and touchscreen temperature controls.
Pros
- Dual heat exchanger with stainless steel and copper
- 0.86 UEF rating with 114,000 BTU/hr output
- Freeze protection using four ceramic heating cores starting at 41°F
- Built-in 3.5-inch LED touchscreen with diagnostic error codes
Cons
- Condensate neutralizer kit is not included
- Maximum output is limited to 5.28 GPM
Good fit if
- You need up to 5.28 GPM to run up to two showers at once.
- You have a natural gas supply line with a 1/2-inch NPT connection.
- You want an indoor unit with digital touchscreen controls and freeze defense.
Skip if
- You need higher output than 5.28 GPM for simultaneous high-demand fixtures.
- You require a liquid propane unit instead of natural gas.
Verdict: Thermomate 5.28 GPM Indoor Natural Gas delivers efficient condensing performance for smaller households using a standard 1/2-inch gas connection. It provides accurate digital control and freeze protection, though larger homes will require higher flow rates.
Rheem Prestige 11 GPM Condensing Water Heater
Best for: high-demand indoor natural gas homes
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 11.0 GPM
- Installation Location
- Indoor
- Dimensions
- 28.7 x 17.3 x 14.8 inches
View on Amazon: Rheem Prestige 11 GPM Condensing Water Heater
You get a high-demand indoor condensing water heater fueled by natural gas. It delivers an 11.0 GPM flow rate, built-in recirculation, and auto-learn programming that tracks usage patterns for peak demand. Integrated leak detection shuts down gas and water if faults occur. It measures 28.7 by 17.3 by 14.8 inches, making it a practical choice if you require high simultaneous hot water volume.
Pros
- High flow rate of 11.0 GPM
- Built-in recirculation with auto-learn usage programming
- Automatic shutdown with water and gas leak detection
- Indoor condensing natural gas design
Cons
- Requires dedicated indoor installation space
- Configured for natural gas rather than propane
- Cabinet depth of 14.8 inches extends out from mounting wall
Good fit if
- You need high simultaneous output up to 11.0 GPM.
- You have an indoor installation site with natural gas service.
- You want built-in recirculation with automated usage learning.
Skip if
- You use liquid propane instead of natural gas.
- You need an exterior outdoor installation.
Verdict: Rheem Prestige 11 GPM Condensing Water Heater delivers an impressive 11.0 GPM capacity alongside integrated recirculation and automated leak shutoff. It is an exceptional indoor natural gas solution for homes with substantial simultaneous hot water demands.
Rinnai 9 GPM Indoor Condensing Natural Gas Heater
Best for: high-demand indoor natural gas setups
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 9 GPM
- Installation Location
- Indoor
- Dimensions
- 31.3 x 11.5 x 18.5 inches
- Weight
- 72.5 pounds
View on Amazon: Rinnai 9 GPM Indoor Condensing Natural Gas Heater
This indoor natural gas condensing water heater delivers up to 9 GPM, enough to supply up to six fixtures at once. It features a 0.97 Uniform Energy Factor and ENERGY STAR certification for efficient gas operation. Built-in Circ-Logic technology supports external recirculation pump pairing. If you need whole-home indoor hot water capacity using natural gas, this unit matches multi-fixture demands.
Pros
- Delivers up to 9 GPM to run up to 6 appliances at once
- 0.97 Uniform Energy Factor with ENERGY STAR certification
- Circ-Logic technology allows scheduled or on-demand recirculation pairing
- 15-year residential warranty on the heat exchanger
Cons
- Requires a separate Controlr module for WiFi monitoring
- Requires an external pump to use recirculation functions
Good fit if
- You run up to six hot water fixtures at the same time
- You have an indoor natural gas connection
- You want a high-efficiency 0.97 UEF condensing system
Skip if
- You plan to mount the unit outdoors
- You fuel your home with propane rather than natural gas
- You want built-in WiFi hardware included out of the box
Verdict: Rinnai 9 GPM Indoor Condensing Natural Gas Heater provides 9 GPM capacity and a 0.97 UEF for high-demand indoor installations. It connects with external recirculation pumps using onboard Circ-Logic control.
A. O. Smith 10 GPM Outdoor Condensing Tankless Heater
Best for: large homes needing outdoor natural gas heating
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 10.0 GPM
- BTU
- 199,000 BTU/hr
- Installation Location
- Outdoor
- Dimensions
- 23.6 x 17.8 x 17.8 inches
View on Amazon: A. O. Smith 10 GPM Outdoor Condensing Tankless Heater
This condensing unit runs on natural gas and mounts outdoors to supply up to 10.0 GPM of continuous hot water with a 199,000 BTU/hr rating. Its 0.94 UEF efficiency rating and commercial-grade copper heat exchanger support three bathrooms in northern regions and up to four in warmer southern climates. It suits you if you need high-volume outdoor hot water delivery without taking up interior space.
Pros
- Delivers up to 10.0 GPM continuous flow rate
- High 0.94 Uniform Energy Factor (UEF) rating
- Commercial-grade copper heat exchanger with 15-year residential warranty
- Includes wall mount temperature remote controller
Cons
- Designed specifically for outdoor installation
- Requires natural gas and does not support propane
- Depth profile measures 17.8 inches and weight is 59 pounds
Good fit if
- You need high output up to 10.0 GPM for a 3- to 4-bathroom home.
- You want an outdoor natural gas setup that saves interior square footage.
- You want an included wall-mounted digital temperature controller.
Skip if
- You require an indoor water heater installation.
- You need a heater compatible with liquid propane.
- You live in a smaller household where 199,000 BTU/hr capacity exceeds your demand.
Verdict: A. O. Smith 10 GPM Outdoor Condensing Tankless Heater delivers 199,000 BTU/hr heating capacity and 10.0 GPM output for demanding multi-bath households. Its 0.94 UEF condensing design and exterior placement provide high energy efficiency while freeing up indoor space.
Takagi Outdoor 8 GPM Natural Gas Water Heater
Best for: outdoor natural gas setups needing 8 GPM
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 8 GPM
- Installation Location
- Outdoor
- Dimensions
- 24.9 x 17.8 x 11.3 inches
- Capacity
- 8 Gallon
View on Amazon: Takagi Outdoor 8 GPM Natural Gas Water Heater
This outdoor condensing unit delivers up to 8 gallons per minute of continuous hot water using natural gas. Because you install it outside, you do not need indoor venting space or complex indoor exhaust ducting. It features electronic ignition with no standing pilot light and meets ultra-low NOx emission standards. If you need an 8 GPM outdoor water heater for your household demands, this unit fits your exterior setup cleanly.
Pros
- 8 GPM flow rate provides high hot water volume
- Outdoor installation eliminates indoor venting requirements
- Meets SCAQMD Rule 1146.2 for ultra-low NOx emissions
- No standing pilot light
Cons
- Outdoor installation only
- Requires a natural gas connection and cannot use propane
Good fit if
- You want an exterior natural gas unit to save indoor utility space.
- You require an 8 GPM flow rate for multiple plumbing fixtures.
- You live in an area that requires ultra-low NOx emission compliance.
Skip if
- You require an indoor water heater installation.
- You use liquid propane rather than natural gas.
Verdict: Takagi 8 GPM Outdoor Natural Gas Tankless Heater provides an exterior condensing solution delivering 8 gallons per minute without requiring indoor exhaust venting. It is a practical fit when you have natural gas hookups outside and need high output.
Rheem 6.8 GPM Outdoor Condensing Water Heater
Best for: outdoor natural gas setups in freezing climates
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 6.8 GPM
- Installation Location
- Outdoor
- Dimensions
- 28.5 x 9.75 x 27.5 inches
- Weight
- 77 pounds
View on Amazon: Rheem 6.8 GPM Outdoor Condensing Water Heater
This condensing outdoor tankless unit supplies up to 6.8 GPM of hot water powered by natural gas. Built for exterior installation, it features built-in freeze protection rated down to -30 degrees and weighs 77 pounds. An integrated safety system shuts down operation upon detecting gas or water leaks. You get a space-saving exterior setup suited for homes needing moderate flow rates without dedicating indoor wall space.
Pros
- Delivers a 6.8 GPM maximum flow rate
- Freeze protection rated down to -30 degrees
- Automatic shutdown on water or gas leak detection
- Outdoor design eliminates indoor venting requirements
Cons
- Outdoor installation only
- Weighs 77 pounds
- Compatible only with natural gas
Good fit if
- You need an exterior natural gas unit delivering up to 6.8 GPM.
- You live in a climate requiring freeze protection down to -30 degrees.
- You want automatic shutoff protection for fuel and water leaks.
Skip if
- You require an indoor water heater.
- You use propane instead of natural gas.
- You require higher flow capacity than 6.8 GPM.
Verdict: Rheem 6.8 GPM Outdoor Condensing Water Heater delivers reliable exterior natural gas performance with built-in leak shutoff and deep freeze protection. It serves households needing moderate flow rates without sacrificing indoor utility space.
Rinnai Commercial 9 GPM Indoor Condensing Water Heater
Best for: commercial indoor natural gas applications
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 9 GPM
- Installation Location
- Indoor
- Dimensions
- 33.9 x 14.8 x 22.1 inches
- Use
- Commercial
View on Amazon: Rinnai Commercial 9 GPM Indoor Condensing Water Heater
This Rinnai unit is an indoor condensing tankless water heater designed for commercial applications. It delivers up to 9 GPM of continuous flow on natural gas, providing the volume you need for multi-fixture operations. The system features Circ-Logic recirculation control, Wi-Fi monitoring, and multiple venting options. It fits your setup if you require high-demand indoor capacity backed by dedicated commercial hardware.
Pros
- High flow rate of up to 9 GPM
- Circ-Logic technology for scheduled recirculation
- Built-in Wi-Fi monitoring capability
- Multiple venting options for indoor installation
Cons
- Manufacturer recommends professional technician installation
- Heavier unit weight at 72.3 pounds
- Configured strictly for natural gas fuel
Good fit if
- You need 9 GPM flow capacity for high-demand commercial hot water needs.
- You want built-in Wi-Fi monitoring and programmable recirculation patterns.
- You have a dedicated natural gas supply ready for indoor venting.
Skip if
- You need a propane-powered or outdoor-rated installation.
- You intend to install the heater yourself without a professional technician.
Verdict: Rinnai Commercial 9 GPM Indoor Condensing Water Heater provides reliable, high-capacity flow with smart recirculation controls for natural gas setups. It is a dependable choice when your application demands heavy daily output from an indoor condensing footprint.
EZ Tankless Ultra HE Natural Gas Water Heater
Best for: smaller homes with natural gas connections
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 3.4 GPM
- Installation Location
- Indoor
- Dimensions
- 27 x 14.5 x 6.5 inches
- Use
- Whole House
View on Amazon: EZ Tankless Ultra HE Natural Gas Water Heater
The EZ Tankless Ultra HE is an indoor natural gas condensing tankless water heater designed for whole-house use. It delivers up to 3.4 GPM at a 45-degree Fahrenheit temperature rise, using exhaust heat to warm incoming water. You can vent it horizontally or vertically using 2-inch Schedule 40 PVC or CPVC pipe. It suits you if you need a natural gas indoor unit for smaller household demands.
Pros
- Condensing design uses exhaust gas to preheat incoming water
- Supports horizontal or vertical venting with 2-inch Schedule 40 PVC/CPVC
- Includes back-draft prevention device and stainless steel horizontal vent pipe
- Digital display included for monitoring operation
Cons
- Flow rate tops out at 3.4 GPM at a 45°F rise
- Limited to natural gas fuel and indoor installation
Good fit if
- You need an indoor condensing natural gas water heater.
- You want to vent through 2-inch Schedule 40 PVC or CPVC piping.
- You have lower simultaneous flow demands up to 3.4 GPM.
Skip if
- You require more than 3.4 GPM for multiple simultaneous fixtures.
- You need an outdoor installation or liquid propane fuel.
Verdict: EZ Tankless Ultra HE Natural Gas Water Heater delivers indoor condensing operation with versatile PVC venting for lower hot water demands. Its 3.4 GPM capacity suits smaller households using natural gas.
Noritz 6.6 GPM Indoor Natural Gas Tankless Heater
Best for: indoor natural gas homes needing 6.6 GPM
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 6.6 GPM
- Installation Location
- Indoor
- Dimensions
- 6.7 × 13.8 × 23.6 inches
- Weight
- 38 pounds
View on Amazon: Noritz 6.6 GPM Indoor Natural Gas Tankless Heater
This Noritz indoor condensing tankless water heater delivers a 6.6 GPM flow rate using natural gas. It supports Schedule 40 PVC pipe and fittings for exhaust venting. The unit weighs 38 pounds and includes a remote thermostat along with a 6-foot power cord. You get a mid-capacity indoor setup designed for standard natural gas connections without requiring specialized metal venting.
Pros
- 6.6 GPM maximum flow rate
- Vents with Schedule 40 PVC pipe and fittings
- Includes remote thermostat and 6-foot power cord
- Compact 38-pound indoor cabinet
Cons
- Indoor installation only
- Configured strictly for natural gas fuel
Good fit if
- You need an indoor condensing heater with a 6.6 GPM flow rate.
- You have an existing natural gas line.
- You want to vent using Schedule 40 PVC pipe.
Skip if
- You require an outdoor installation.
- You use liquid propane instead of natural gas.
- You need higher output than 6.6 GPM for simultaneous fixtures.
Verdict: Noritz 6.6 GPM Indoor Natural Gas Tankless Heater provides mid-tier condensing performance with convenient Schedule 40 PVC venting compatibility. It handles moderate household hot water needs using standard indoor natural gas connections.
Rinnai 9 GPM Outdoor Propane Condensing Heater
Best for: outdoor propane setups needing built-in recirculation
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Propane
- Flow Rate
- 9 GPM
- Installation Location
- Outdoor
- Dimensions
- 33.9 x 14.8 x 22.1 inches
- Weight
- 80.9 pounds
View on Amazon: Rinnai 9 GPM Outdoor Propane Condensing Heater
This condensing water heater runs on propane and installs outdoors, saving interior wall space. You get up to a 9 GPM flow rate, suitable for multiple simultaneous taps. It includes built-in ThermaCirc360 recirculation with an integrated pump, timer, and thermal bypass valve for setups lacking dedicated return lines. It suits outdoor propane installations needing high capacity and faster hot water delivery.
Pros
- Up to 9 GPM hot water flow rate
- Built-in recirculation pump, timer, and thermal bypass valve
- Outdoor installation eliminates indoor venting runs
- Includes Wi-Fi monitoring capability
Cons
- Outdoor installation only
- Discontinued model according to manufacturer specs
- Requires propane fuel supply
Good fit if
- You need an outdoor propane unit delivering up to 9 GPM.
- You want built-in recirculation without a dedicated return line.
Skip if
- You need an indoor water heater.
- You use natural gas instead of propane.
Verdict: Rinnai 9 GPM Outdoor Propane Condensing Heater provides high hot water volume alongside built-in recirculation hardware for outdoor setups. It delivers strong flow without taking up interior utility space.
Rinnai Indoor Propane Condensing Tankless Water Heater
Best for: High-flow propane homes with space limits
- Venting Type
- Condensing (what this guide is about)
- Fuel Type
- Propane
- Flow Rate
- Up to 9 GPM
- BTU
- 160,000 BTU
- Installation Location
- Indoor
- Dimensions
- 9 x 9 x 9 inches
View on Amazon: Rinnai Indoor Propane Condensing Tankless Water Heater
The Rinnai RSC160iP is an indoor condensing tankless water heater designed for propane. It delivers up to 9 GPM with 160,000 BTU of power. Smart-Circ technology learns your usage patterns to schedule recirculation for efficiency. The unit is compact, measuring 9 by 9 by 9 inches, and weighs 78 pounds. It is ENERGY STAR qualified with a Uniform Energy Factor of 0.110. This model suits homes needing high flow rates in a small footprint.
Pros
- High flow rate of up to 9 GPM
- Smart-Circ recirculation learns usage patterns
- Compact 9x9x9 inch design
- 160,000 BTU output
Cons
- Requires separate Controlr module for WiFi
- Propane only, not natural gas
- 78 pounds weight
Good fit if
- You need high flow for multiple fixtures
- You have propane fuel available
- You want compact indoor installation
Skip if
- You use natural gas
- You need built-in WiFi control
- You prefer outdoor installation
Verdict: Rinnai RSC160iP Propane Condensing Heater offers high flow and smart efficiency for propane users. It fits homes with space constraints and high hot water demands.
Specifications side by side
| Spec | Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater | Ranein 5.1 GPM Condensing Natural Gas Water Heater | VancEpic 5.1 GPM Propane Condensing Water Heater | Rinnai I-SERIES Plus Condensing Combi Boiler | Thermomate 5.28 GPM Indoor Natural Gas | Rheem Prestige 11 GPM Condensing Water Heater | Rinnai 9 GPM Indoor Condensing Natural Gas Heater | A. O. Smith 10 GPM Outdoor Condensing Tankless Heater | Takagi Outdoor 8 GPM Natural Gas Water Heater | Rheem 6.8 GPM Outdoor Condensing Water Heater | Rinnai Commercial 9 GPM Indoor Condensing Water Heater | EZ Tankless Ultra HE Natural Gas Water Heater | Noritz 6.6 GPM Indoor Natural Gas Tankless Heater | Rinnai 9 GPM Outdoor Propane Condensing Heater | Rinnai Indoor Propane Condensing Tankless Water Heater |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Type | Propane or Natural Gas | Natural Gas | Propane | Natural Gas or Propane | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Propane | Propane |
| Flow Rate | 11.1 GPM | 5.1 GPM | 5.1 GPM | not specified | 5.28 GPM | 11.0 GPM | 9 GPM | 10.0 GPM | 8 GPM | 6.8 GPM | 9 GPM | 3.4 GPM | 6.6 GPM | 9 GPM | Up to 9 GPM |
| BTU | not specified | 120,000 BTU | 120,000 BTU/hr | 175K BTU / DHW 199K BTU | 114,000 BTU/hr | not specified | not specified | 199,000 BTU/hr | not specified | not specified | not specified | not specified | not specified | not specified | 160,000 BTU |
| Installation Location | Indoor/Outdoor | not specified | Indoor | Indoor | Indoor | Indoor | Indoor | Outdoor | Outdoor | Outdoor | Indoor | Indoor | Indoor | Outdoor | Indoor |
| Voltage | not specified | 120 V | not specified | not specified | 120 V | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified |
| Temperature Control | not specified | 95°F to 149°F, ±1°F | 95°F to 149°F | not specified | 90°F to 140°F | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified |
| Certification | not specified | ANSI Z21.10.3 | not specified | 96% AFUE | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified |
| Dimensions | 30.1 x 18.5 x 30.1 inches | 22 x 14.2 x 6.4 inches | 9.25 x 20.2 x 20.2 inches | 45.3 x 19.5 x 19.5 inches | 21 x 13 x 7 inches | 28.7 x 17.3 x 14.8 inches | 31.3 x 11.5 x 18.5 inches | 23.6 x 17.8 x 17.8 inches | 24.9 x 17.8 x 11.3 inches | 28.5 x 9.75 x 27.5 inches | 33.9 x 14.8 x 22.1 inches | 27 x 14.5 x 6.5 inches | not specified | 33.9 x 14.8 x 22.1 inches | 9 x 9 x 9 inches |
| Use | not specified | not specified | not specified | Boiler | not specified | not specified | not specified | not specified | not specified | not specified | Commercial | Whole House | not specified | not specified | not specified |
| Venting Type | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing | Condensing |
| Capacity | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | 8 Gallon | not specified | not specified | not specified | not specified | not specified | not specified |
| Features | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | not specified | Digital Display | not specified | not specified | not specified |
| Weight | 55 pounds | 26 pounds | not specified | 79.4 pounds | 26 pounds | not specified | 72.5 pounds | 59 pounds | not specified | 77 pounds | 72.3 pounds | not specified | 38 pounds | 80.9 pounds | 78 pounds |
| Size | 11.1 GPM | not specified | 5.1GPM, 120,000BTU, LPG | 175K BTU / DHW 199K BTU | not specified | 11 GPM | 9 GPM | not specified | Medium | not specified | not specified | not specified | 13.8 inches (W) x 23.6 inches (H) x 10 inches (D) | 9 GPM | not specified |
| Color | Silver | Gray | Condensing | Gray | Silver | Gray | Silver | White | White | Gray | CU160in - Natural Gas/9 GPM | White | White | Outdoor Installation | Gray |
| Model | RX199iN | RH12KG-C-NG | RH12KG-C-LPG | IP175199C | CZ480NG | RTGH-RH11DVLN | RU160in | ATO-540H-N 100 | T-H3S-OS-N | RTGH-68XLN-2 | CU160iN | EZ Ultra HE | NRC661-DV-NG | RUR160ep | RSC160iP |
Is Condensing Technology Worth the Upgrade?
Condensing units capture exhaust heat to raise efficiency. You get higher UEF or AFUE ratings, which lowers energy use. This process creates acidic condensate, so you need a drain line. Most indoor models use PVC venting instead of metal. This allows flexible placement. Outdoor units like the A. O. Smith 10 GPM shed this water naturally. You must ensure your installation site handles the byproducts.
Worth it if
- You want maximum energy efficiency from natural gas or propane
- You can install a PVC vent pipe and a condensate drain
- You need high flow rates without large metal venting requirements
Skip it if
- You cannot run a drain line to remove acidic condensate
- You are replacing an existing unit with incompatible venting
- You prefer simpler non-condensing models with fewer installation steps
You might also want to browse our list of the best desk space heaters for your office.
How we selected condensing units
We identified condensing models by checking Amazon listings for the Venting Type: Condensing specification in the title or feature list. We pulled every detail from those published spec sheets. We did not handle or test any hardware. All information comes directly from the manufacturer data provided on the product pages.
We ordered the 15 picks by availability first. Then we sorted by overall rating weighted by rating count. Finally, we ranked by how many guide criteria the specs meet. We show only one variant per product family. Prices and stock levels refresh daily on the page.
How to choose the right condensing unit
-
Match GPM to bathroom count
Flow rate determines how many fixtures run simultaneously. Check the GPM spec to ensure adequate supply. The Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater supports large homes with high demand. Smaller households should consider the Thermomate 5.28 GPM Indoor Natural Gas, which suits one- to two-bath setups. Avoid undersizing, as low flow causes pressure drops when multiple taps are open. Match the highest concurrent usage to the rated capacity.
-
Select fuel type carefully
Condensing units require specific fuel connections. Natural gas is common for indoor utility rooms. Propane offers flexibility for rural areas or outdoor installs. The VancEpic 5.1 GPM Propane Condensing Water Heater is designed for LPG supply lines. You must verify your existing fuel infrastructure before purchasing. Mismatched fuel types prevent operation. Check the Fuel Type attribute in the product data to confirm compatibility with your home’s energy source.
-
Plan for indoor or outdoor
Installation location affects venting and space needs. Indoor models like the Rinnai 9 GPM Indoor Condensing Natural Gas Heater require interior exhaust routing. Outdoor units, such as the A. O. Smith 10 GPM Outdoor Condensing Tankless Heater, free up indoor space but need weather protection. Verify the Installation Location spec. Indoor units often use PVC venting. Outdoor units withstand environmental exposure. Choose based on available utility space and local climate conditions.
-
Check venting requirements
Condensing technology produces acidic exhaust that requires specific venting. Most indoor models use standard PVC pipe, simplifying installation. The Noritz 6.6 GPM Indoor Natural Gas Tankless Heater supports Schedule 40 PVC venting. You must ensure your setup includes proper condensate drainage. Outdoor units may have different venting constraints. Always review the Venting Type specification. Improper venting leads to efficiency loss or safety hazards. Plan your exhaust route before finalizing your purchase.
-
Consider combi boiler needs
Some units provide both space heating and hot water. The Rinnai I-SERIES Plus Condensing Combi Boiler delivers 96% AFUE efficiency for combined use. This option replaces standalone boilers and water heaters. It suits homes needing central heating alongside domestic hot water. Check the Use attribute to identify combi models. These units often have higher BTU outputs, such as 199,000 BTU for domestic hot water. Evaluate your heating and hot water demands together to determine if a combi unit saves space.
Frequently asked questions
Can I install a condensing tankless water heater outdoors?
Yes, provided you select a model rated for exterior placement. The A. O. Smith 10 GPM and Takagi 8 GPM units are designed for outdoor use. These models handle weather exposure and do not require indoor exhaust venting. Always verify the installation location specification in the product data before mounting.
What is the difference between indoor and outdoor condensing units?
Indoor units require specific venting paths, often using PVC pipes, and need interior space for condensate drainage. Outdoor models, like the Rheem 6.8 GPM, are built to withstand elements and free up indoor utility space. You must match the unit to your available mounting location and gas line access.
Do condensing tankless heaters need special venting?
Condensing units capture exhaust heat, which creates acidic condensate. Most indoor models use standard Schedule 40 PVC venting instead of heavy metal pipes. This allows for flexible installation near the gas source. Ensure your home has the necessary venting materials and a drain line for the condensate.
Which condensing water heater has the highest flow rate?
The Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater offers the highest capacity at 11.1 gallons per minute. This flow rate supports large homes with multiple simultaneous fixtures. The Rheem Prestige 11 GPM model is a close alternative for high-demand indoor natural gas setups requiring substantial hot water volume.
Can I use propane with a condensing tankless heater?
Yes, several models support propane fuel sources. The VancEpic 5.1 GPM and Rinnai 9 GPM Outdoor Propane units are designed for LPG. You must verify the fuel type specification on the listing. Propane units are suitable for homes without natural gas lines or for specific outdoor applications.
How do I know if a condensing unit is a boiler?
Check the use specification in the product data. The Rinnai I-SERIES Plus is listed as a boiler. It provides both home heating and domestic hot water in one 96% AFUE unit. Standard tankless heaters only provide hot water for sinks and showers. Select based on your heating needs.
Do condensing tankless heaters include recirculation features?
Some models integrate recirculation controls to reduce wait times for hot water. The Rheem Prestige 11 GPM includes integrated recirculation and leak shutoff. The Rinnai 9 GPM Indoor model uses onboard Circ-Logic control to connect with external pumps. Check the attributes for these specific hardware inclusions.