9 Best Rinnai Indoor Tankless Water Heaters, Compared
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Finding the best Rinnai indoor tankless water heaters requires checking published specs carefully. We compared 9 models to help you choose. The top pick is the Rinnai 8.5 GPM Indoor Propane Tankless Water Heater, which leads because it offers a high 8.5 GPM flow rate for indoor propane setups. All selections are based strictly on the specifications published on the listings. This guide helps you decide which unit fits your home’s hot water needs and venting requirements.
Quick picks
The best fit for you
- You need high flow for indoor propane setups Rinnai 8.5 GPM Indoor Propane Tankless Water Heater It delivers 8.5 GPM flow with a compact 14.1-inch width for easy indoor installation.
- You want the most compact model on the list Rinnai Indoor Propane Condensing Tankless Water Heater Its 9x9x9-inch footprint is the smallest dimension set among all listed indoor propane units.
- You need built-in recirculation for natural gas homes Rinnai Smart-Circ 6.1 GPM Natural Gas Heater It combines 6.6 GPM flow with integrated recirculation in a lightweight 51-pound cabinet.
- You run multiple fixtures simultaneously in large homes Rinnai 9 GPM Indoor Condensing Natural Gas Heater It provides 9 GPM output paired with a 0.97 UEF rating for high demand.
Our 9 picks
Rinnai 8.5 GPM Indoor Propane Tankless Water Heater
Best for: indoor propane setups requiring high flow rates
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Propane
- Flow Rate
- 8.5 GPM
- BTU
- 180k BTU
- Dimensions
- 27.3 x 14.1 x 10.8 inches
- Venting Type
- Non-Condensing
View on Amazon: Rinnai 8.5 GPM Indoor Propane Tankless Water Heater
The Rinnai RE180iP is an indoor, non-condensing tankless water heater fueled by propane. It delivers a maximum flow rate of 8.5 GPM, which supports up to seven fixtures at once. Measuring 27.3 by 14.1 by 10.8 inches and weighing 53.8 pounds, it fits compact interior spaces. An integrated LED screen displays service reminders and error codes. This unit suits you if you require high hot water capacity from an indoor propane hookup.
Pros
- Delivers up to 8.5 GPM flow rate to supply up to 7 fixtures at once
- Built-in LED screen provides error codes and routine service reminders
- Compact 27.3 by 14.1 by 10.8-inch frame fits confined indoor areas
- Includes up to 15-year heat exchanger and 5-year parts and labor warranty with 90-day registration
Cons
- Uses non-condensing venting rather than condensing technology
- Requires separate purchase of the Controlr module for Wi-Fi capability
- Labor warranty drops to 1 year if not registered within 90 days
Good fit if
- You have an indoor propane supply line ready for installation.
- You run multiple water fixtures at once and need up to 8.5 GPM capacity.
- You want on-unit LED diagnostics for system status and troubleshooting.
Skip if
- You need a heater powered by natural gas.
- You plan to mount your water heater in an outdoor location.
- You want built-in Wi-Fi controls included without extra hardware.
Verdict: Rinnai RE180iP 8.5 GPM Propane Tankless Heater provides indoor hot water delivery of up to 8.5 GPM for propane-equipped households. Its compact footprint and LED diagnostic panel offer straightforward operation and servicing.
Rinnai RUCS65IP Propane 6.5 GPM
Best for: Indoor propane setups needing flexible venting
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Propane
- Flow Rate
- 6.5 GPM
- Dimensions
- 14.5" W x 22" D x 35" H
- Weight
- 62 pounds
The Rinnai RUCS65iP is an indoor propane tankless water heater designed for continuous hot water. It delivers a flow rate of up to 6.5 GPM, serving multiple appliances simultaneously. Its compact dimensions of 14.5 by 22 inches and 62-pound weight allow for flexible placement. This unit offers multiple venting options, including PVC/CPVC, making it suitable for various indoor installation layouts. It is built for durability with a 12-year heat exchanger warranty.
Pros
- Provides up to 6.5 GPM flow rate for high-demand usage
- Compact size fits in tight indoor spaces
- Flexible venting options including PVC/CPVC compatibility
- 12-year residential warranty on the heat exchanger
Cons
- Lower flow rate compared to 9 GPM models on this list
- Requires professional installation for proper setup
- Limited to propane fuel type only
Good fit if
- You need a reliable propane heater for indoor use
- You want flexible venting options for your layout
- You prioritize long-term heat exchanger coverage
Skip if
- You require natural gas fuel
- You need a flow rate above 6.5 GPM
- You prefer a self-installable unit
Verdict: Rinnai RUCS65iP Propane Indoor Heater suits homeowners who need a durable, compact propane solution with flexible venting. It is ideal for those who value long-term warranty coverage over maximum flow capacity.
Rinnai Smart-Circ 6.1 GPM Natural Gas Heater
Best for: Indoor homes needing built-in recirculation
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 6.6 GPM
- Dimensions
- 27.3 x 14.1 x 10.8 inches
- Weight
- 51 pounds
View on Amazon: Rinnai Smart-Circ 6.1 GPM Natural Gas Heater
This indoor natural gas tankless water heater delivers up to a 6.6 GPM flow rate. It features built-in Smart-Circ intelligent recirculation that tracks your routine and schedules hot water delivery. Measuring 27.3 by 14.1 by 10.8 inches and weighing 51 pounds, it fits compact indoor spaces. This unit suits you if you run multiple fixtures simultaneously on natural gas and want built-in recirculation.
Pros
- Built-in Smart-Circ pump learns usage patterns and schedules recirculation
- Provides up to 6.6 GPM flow rate for indoor installations
- Compact dimensions of 27.3 x 14.1 x 10.8 inches at 51 pounds
- 15-year heat exchanger warranty and 5-year parts warranty
Cons
- WiFi control requires a separate Controlr module
- Labor warranty defaults to 1 year unless registered within 90 days
Good fit if
- You use natural gas for your indoor water heating.
- You want scheduled recirculation without installing an external pump.
- You need to supply hot water for multiple fixtures at up to 6.6 GPM.
Skip if
- You require factory-included WiFi hardware.
- You need a propane-fueled indoor water heater.
- You need higher capacity than 6.6 GPM for your fixtures.
Verdict: Rinnai Smart-Circ 6.6 GPM Natural Gas Heater combines integrated recirculation with a 6.6 GPM flow rate for indoor natural gas setups. It delivers scheduled circulation in a compact 51-pound suitcase-sized cabinet.
Rinnai Commercial 9 GPM Indoor Condensing Water Heater
Best for: indoor commercial facilities needing high flow
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 9 GPM
- Dimensions
- 33.9 x 14.8 x 22.1 inches
- Use
- Commercial
- Venting Type
- Condensing
View on Amazon: Rinnai Commercial 9 GPM Indoor Condensing Water Heater
This indoor condensing tankless unit provides commercial-grade hot water powered by natural gas. You get a flow rate of up to 9 GPM, which supports heavy simultaneous water use. It features Circ-Logic recirculation control and Wi-Fi monitoring capabilities. Built for commercial installations, it measures 33.9 by 14.8 by 22.1 inches and weighs 72.3 pounds. It suits your facility if you need high capacity with dedicated commercial warranty coverage.
Pros
- High flow rate of 9 GPM for commercial demands
- Circ-Logic technology for controlled recirculation patterns
- Wi-Fi monitoring capability for demand tracking
- Commercial warranty covering 8 years on heat exchanger, 5 years on parts, and 1 year on labor
Cons
- Requires professional technician installation
- Heavier unit at 72.3 pounds requiring solid wall support
- Restricted to natural gas supply lines
Good fit if
- You operate a commercial facility needing up to 9 GPM of continuous hot water.
- You have dedicated indoor natural gas supply lines and condensing venting access.
- You need automated recirculation scheduling and remote Wi-Fi monitoring.
Skip if
- You require liquid propane instead of natural gas.
- You need an outdoor-rated installation rather than an indoor unit.
Verdict: Rinnai Commercial Condensing 9 GPM Water Heater delivers high-volume performance for indoor commercial applications requiring smart recirculation and remote monitoring.
Rinnai 9 GPM Indoor Condensing Natural Gas Water Heater
Best for: homes without dedicated hot water return lines
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 9 GPM
- Dimensions
- 31.3 x 18.5 x 11.4 inches
- Venting Type
- Condensing
- Weight
- 82.5 pounds
View on Amazon: Rinnai 9 GPM Indoor Condensing Natural Gas Water Heater
This indoor condensing unit delivers up to 9 GPM of hot water using natural gas. It features built-in ThermaCirc360 recirculation with an internal pump, timer, and thermal bypass valve for homes without dedicated return lines. Measuring 31.3 by 18.5 by 11.4 inches, it provides Wi-Fi monitoring and residential coverage lasting up to 15 years. You get high flow suited for households needing faster hot water delivery.
Pros
- Delivers up to 9 GPM hot water flow rate
- Includes built-in recirculation pump, timer, and thermal bypass valve
- Features Wi-Fi monitoring capability
- Offers 15-year heat exchanger residential warranty
Cons
- Discontinued model replaced by RSC160iN
- Weighs 82.5 pounds
- Parts warranty coverage lasts only 1 year
Good fit if
- You need up to 9 GPM flow powered by natural gas.
- You lack a dedicated return line and want built-in recirculation.
- You want indoor condensing technology with Wi-Fi monitoring.
Skip if
- You prefer an active, non-discontinued product line.
- You require propane instead of natural gas.
- You want longer than 1-year coverage on parts.
Verdict: Rinnai 9 GPM Indoor Condensing Natural Gas Water Heater provides high flow and integrated recirculation hardware for homes without dedicated return plumbing. It remains a capable condensing option, though the manufacturer has marked it as discontinued.
Rinnai Indoor Propane Condensing Tankless Water Heater
Best for: Propane homes needing multi-fixture automated recirculation
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Propane
- Flow Rate
- Up to 9 GPM
- BTU
- 160,000 BTU
- Dimensions
- 9 x 9 x 9 inches
- Venting Type
- Condensing
View on Amazon: Rinnai Indoor Propane Condensing Tankless Water Heater
This indoor condensing tankless water heater runs on propane and delivers up to 9 GPM, supporting up to six fixtures at once. It produces up to 160,000 BTU and features built-in Smart-Circ intelligent recirculation that learns your daily hot water habits to schedule the pump. If you have a propane-powered home needing simultaneous hot water for multiple fixtures and want automated recirculation, this compact unit fits your indoor installation.
Pros
- Delivers up to 9 GPM to supply up to six fixtures simultaneously
- Smart-Circ technology learns usage patterns to automate pump recirculation
- Provides up to 160,000 BTU heating output with condensing efficiency
- Includes 15-year heat exchanger, 5-year labor, and 1-year parts residential coverage
Cons
- Requires purchasing the Controlr module separately for WiFi functionality
- Operates strictly on propane rather than natural gas
- Heavier unit at 78 pounds
Good fit if
- You use propane fuel and require an indoor condensing water heater.
- You need high flow rates up to 9 GPM across multiple fixtures.
- You want built-in recirculation scheduling based on your water usage patterns.
Skip if
- You need a natural gas connection rather than propane.
- You want integrated WiFi connectivity without buying add-on hardware.
- You require a water heater designed for outdoor installation.
Verdict: Rinnai Smart-Circ 9 GPM Propane Tankless Water Heater provides 160,000 BTU and automated recirculation for homes operating on indoor propane. It supplies up to six fixtures at once while adapting to your household hot water habits.
Rinnai 6.5 GPM Indoor Propane Tankless Water Heater
Best for: propane homes running up to five fixtures
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Propane
- Flow Rate
- 6.5 GPM
- Dimensions
- 14 × 9.27 × 26.9 inches
- Weight
- 45.6 pounds
View on Amazon: Rinnai 6.5 GPM Indoor Propane Tankless Water Heater
This indoor tankless water heater runs on propane and delivers a maximum flow rate of 6.5 GPM, allowing you to supply hot water to up to five appliances at once. It measures 26.9 inches high by 14 inches long and weighs 45.6 pounds. With integrated scale detection to protect the unit from long-term damage, this model suits mid-sized propane-equipped households needing dedicated indoor hot water capacity.
Pros
- Maximum flow rate of up to 6.5 GPM
- Powers up to 5 appliances simultaneously
- Enhanced scale detection reduces long-term damage risk
- Compact 45.6-pound indoor chassis
Cons
- Propane fuel only without native natural gas support
- Requires professional technician installation
- Flow rate capped at 6.5 GPM
Good fit if
- You use propane as your home fuel source.
- You need to supply hot water for up to 5 fixtures at once.
- You want an indoor unit with built-in scale detection.
Skip if
- You have a natural gas hookup rather than propane.
- You intend to install the unit without hiring a professional technician.
- You need flow rates higher than 6.5 GPM for high-demand setups.
Verdict: Rinnai 6.5 GPM Indoor Propane Tankless Water Heater delivers steady indoor hot water for propane homes running multiple fixtures simultaneously. Its built-in scale detection and 45.6-pound footprint make it a balanced choice for moderate indoor demands.
Rinnai 9 GPM Indoor Condensing Natural Gas Heater
Best for: large homes running multiple fixtures at once
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- 9 GPM
- Dimensions
- 31.3 x 11.5 x 18.5 inches
- Venting Type
- Condensing
- Weight
- 72.5 pounds
View on Amazon: Rinnai 9 GPM Indoor Condensing Natural Gas Heater
This indoor condensing tankless water heater delivers up to 9 GPM using natural gas, which can supply up to six appliances at once. It features an energy-efficient 0.97 Uniform Energy Factor and integrates Circ-Logic technology for scheduled or on-demand recirculation. If you have a large household with high peak hot water demands and natural gas service, this unit provides continuous hot water across multiple fixtures simultaneously.
Pros
- Up to 9 GPM flow rate supports up to six appliances at once
- High efficiency with a 0.97 Uniform Energy Factor and ENERGY STAR certification
- Circ-Logic technology enables scheduled or on-demand recirculation
- Long residential warranty coverage with 15 years on the heat exchanger
Cons
- Controlr Wi-Fi monitoring module is not included
- Requires an external pump for recirculation operation
- Heavy unit at 72.5 pounds
Good fit if
- You need to run up to six hot water appliances at the same time.
- You have an indoor natural gas connection and prioritize a high 0.97 UEF rating.
- You want Circ-Logic controls to manage an external recirculation pump.
Skip if
- You use liquid propane rather than natural gas for your home heating.
- You want built-in Wi-Fi controls out of the box without buying an add-on module.
- You require an outdoor installation rather than an indoor mount.
Verdict: Rinnai 9 GPM Condensing Natural Gas Water Heater pairs a high 9 GPM output with an efficient 0.97 UEF rating for busy indoor setups. It serves high-demand homes that need reliable multi-fixture capacity from natural gas.
Rinnai 9 GPM Indoor Natural Gas Tankless Water Heater
Best for: Multi-fixture indoor natural gas recirculation setups
- Installation Location
- Indoor (what this guide is about)
- Fuel Type
- Natural Gas
- Flow Rate
- Up to 9 GPM
- BTU
- 160,000 BTU/hr
- Dimensions
- 33.9 x 21.3 x 14.4 inches
- Venting Type
- Condensing
View on Amazon: Rinnai 9 GPM Indoor Natural Gas Tankless Water Heater
This indoor condensing tankless unit runs on natural gas and delivers up to 9 GPM across up to six fixtures at once. It burns up to 160,000 BTU per hour and uses built-in Smart-Circ technology to learn your daily water usage and automate recirculation. It suits your home if you need whole-house capacity with automated recirculation and have an indoor natural gas connection ready.
Pros
- Delivers up to 9 GPM to supply up to six fixtures at once
- Smart-Circ technology learns usage patterns to automate recirculation
- Provides up to 160,000 BTU per hour heat output
- Includes 15-year heat exchanger and 5-year labor residential warranties
Cons
- Requires a separate Controlr module for WiFi connectivity
- Operates strictly on natural gas rather than propane
- Unit weighs 66 pounds and requires professional indoor mounting
Good fit if
- You have an indoor natural gas supply line ready for installation.
- You run up to six plumbing fixtures simultaneously.
- You want automated recirculation that adapts to your household schedule.
Skip if
- You heat your water using liquid propane.
- You want built-in WiFi controls included without purchasing extra modules.
Verdict: Rinnai Smart-Circ Condensing Natural Gas Tankless Heater provides high-volume indoor heating up to 9 GPM with built-in pattern-learning recirculation. It gives multi-fixture households an efficient natural gas option backed by dedicated factory warranty terms.
Specifications side by side
| Spec | Rinnai 8.5 GPM Indoor Propane Tankless Water Heater | Rinnai RUCS65IP Propane 6.5 GPM | Rinnai Smart-Circ 6.1 GPM Natural Gas Heater | Rinnai Commercial 9 GPM Indoor Condensing Water Heater | Rinnai 9 GPM Indoor Condensing Natural Gas Water Heater | Rinnai Indoor Propane Condensing Tankless Water Heater | Rinnai 6.5 GPM Indoor Propane Tankless Water Heater | Rinnai 9 GPM Indoor Condensing Natural Gas Heater | Rinnai 9 GPM Indoor Natural Gas Tankless Water Heater |
|---|---|---|---|---|---|---|---|---|---|
| Fuel Type | Propane | Propane | Natural Gas | Natural Gas | Natural Gas | Propane | Propane | Natural Gas | Natural Gas |
| Flow Rate | 8.5 GPM | 6.5 GPM | 6.6 GPM | 9 GPM | 9 GPM | Up to 9 GPM | 6.5 GPM | 9 GPM | Up to 9 GPM |
| BTU | 180k BTU | not specified | not specified | not specified | not specified | 160,000 BTU | not specified | not specified | 160,000 BTU/hr |
| Installation Location | Indoor | not specified | Indoor | Indoor | Indoor | Indoor | Indoor | Indoor | Indoor |
| Dimensions | 27.3 x 14.1 x 10.8 inches | 14.5" W x 22" D x 35" H | 27.3 x 14.1 x 10.8 inches | 33.9 x 14.8 x 22.1 inches | 31.3 x 18.5 x 11.4 inches | 9 x 9 x 9 inches | not specified | 31.3 x 11.5 x 18.5 inches | 33.9 x 21.3 x 14.4 inches |
| Use | not specified | not specified | not specified | Commercial | not specified | not specified | not specified | not specified | not specified |
| Venting Type | Non-Condensing | not specified | not specified | Condensing | Condensing | Condensing | not specified | Condensing | Condensing |
| Weight | 53.8 pounds | 62 pounds | 51 pounds | 72.3 pounds | 82.5 pounds | 78 pounds | 45.6 pounds | 72.5 pounds | 66 pounds |
| Size | 8.5 GPM | 6.5 GPM | 6.6 GPM | not specified | 9 GPM | not specified | 6.5 GPM | 9 GPM | not specified |
| Color | Silver | White | Silver | CU160in - Natural Gas/9 GPM | Silver | Gray | White | Silver | Gray |
| Model | REU-VE2432FFD-US-P | RUCS65iP | REU-VEP2125FFD-US-N | CU160iN | RUR160iN | RSC160iP | V65iP | RU160in | RSC160iN |
If you evaluate other dedicated indoor heat systems, specifications for the best indoor saunas cover electrical loads and cabinet dimensions.
Check Fuel Type and Venting Needs
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Verify Your Fuel Source
Start by confirming whether your home uses natural gas or propane. The Rinnai RE180iP runs on propane and delivers 8.5 GPM, making it ideal for propane-equipped households. In contrast, the RUR160iN uses natural gas and offers 9 GPM flow for larger homes. Selecting the wrong fuel type can prevent installation entirely. Always match the unit’s fuel specification to your existing supply line before purchasing to ensure compatibility and safe operation.
-
Understand Venting Requirements
Venting type dictates where you can place the unit. The REU-VE2432FFD-US-P uses non-condensing venting, which often requires specific clearance and pipe routing. Conversely, condensing models like the RSC160iP or RUR160iN handle moisture differently, allowing for more flexible installation in certain indoor spaces. Check the venting spec in the data sheet. This detail affects your contractor’s ability to route exhaust pipes efficiently through your home’s structure.
-
Match Flow to Fixture Count
Higher flow rates support more simultaneous fixtures. The CU160iN provides 9 GPM, suitable for commercial facilities or large homes with multiple bathrooms running at once. Smaller units like the V65iP offer 6.5 GPM, which suffices for moderate indoor demands. Compare the GPM spec against your household’s peak usage. If you often run showers and dishes together, choose a higher GPM model to avoid temperature drops.
-
Consider Built-in Recirculation
Some models include integrated recirculation pumps to reduce wait times. The REU-VEP2125FFD-US-N features Smart-Circ technology for scheduled circulation without extra hardware. This is useful for homes without dedicated return lines. The RSC160iP also offers automated recirculation for up to six fixtures. Check if the unit includes this feature in the attributes. It simplifies installation by eliminating the need for separate pump systems and additional plumbing work.
-
Check Physical Dimensions
Indoor spaces are often limited. The RSC160iP has a compact 9x9x9-inch footprint, fitting into tight closets or utility rooms. The RUR160iN is wider at 18.5 inches but still fits standard indoor enclosures. Measure your installation area before buying. Compare the width, height, and length specs in the data. Ensuring the unit fits physically prevents costly returns and installation delays during the setup phase.
Frequently asked questions
Which Rinnai indoor tankless water heater has the highest flow rate?
The Rinnai Commercial 9 GPM Indoor Condensing Water Heater and the RUR160iN both provide 9 GPM output. These models are designed for high-demand households or commercial facilities. The CU160iN model weighs 72.3 pounds, while the RUR160iN weighs 82.5 pounds. Both units deliver substantial hot water volume for multiple simultaneous fixtures.
Are there Rinnai indoor units that run on propane?
Yes, several Rinnai indoor models operate on propane. The RE180iP delivers 8.5 GPM and uses non-condensing venting. The RUCS65iP offers 6.5 GPM with a white finish. The V65iP also provides 6.5 GPM in a compact white cabinet. The RSC160iP model supplies 9 GPM using propane fuel for indoor installation.
Which model is the most compact for indoor installation?
The RSC160iP propane model is the most compact, measuring 9 inches in width, height, and length. It weighs 78 pounds. This small footprint makes it suitable for tight indoor spaces. Other models like the RE180iP measure 14.1 by 10.8 by 27.3 inches, which is larger but still relatively slim for indoor mounting.
Do any Rinnai indoor heaters include built-in recirculation?
Several models feature integrated recirculation capabilities. The Smart-Circ 6.6 GPM Natural Gas Heater includes scheduled circulation. The CU160iN commercial unit offers smart recirculation with remote monitoring. The RSC160iP propane model provides automated recirculation for up to six fixtures. These features help reduce hot water wait times without needing separate return lines.
What is the difference between condensing and non-condensing venting?
Condensing models, like the RUR160iN and CU160iN, capture heat from exhaust gases for higher efficiency. They typically use PVC venting. Non-condensing units, such as the RE180iP, require metal venting and operate at lower efficiency. Condensing units are generally heavier, with the RUR160iN weighing 82.5 pounds compared to the lighter non-condensing options.
Which Rinnai heater is best for a large household?
For large households, the 9 GPM models are ideal. The RUR160iN natural gas unit provides 9 GPM with a 0.97 UEF rating. The RSC160iN propane model also delivers 9 GPM with pattern-learning recirculation. These high-flow units can serve multiple bathrooms and appliances simultaneously, ensuring consistent hot water supply during peak usage times.