11 Condensing Vs Non Condensing Tankless Water Heater of 2026 To Avoid Installation Surprises

1

Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water

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  9.7
• Brand
  Rheem

Key specs2

Venting Requirement

None required (outdoor mount)

Groundwater Flow Rating

Delivers up to 8.4 GPM at a 35-degree rise on natural gas, making it suitable for multi-bathroom homes where exterior mounting is feasible.

Pros & cons43

Pros

• Outdoor design eliminates costly indoor venting cuts and exhaust pipe runs
• Delivers 8.4 GPM at a 35-degree Fahrenheit rise to run 3 to 4 showers at once
• Built-in digital control panel allows direct adjustments in 1-degree increments
• Metal exterior cabinet includes freeze protection for outdoor weather resistance

Cons

• Outdoor-only installation cannot be placed inside a mechanical closet or basement
• Non-condensing 0.82 UEF rating offers lower thermal efficiency than condensing units
• Does not include WiFi connectivity for remote temperature adjustments or monitoring

2

Rinnai RE199eP Non-Condensing Propane Tankless Water Heater, Up to 9.8

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  9.6
• Brand
  Rinnai

Key specs2

Outdoor Gas Setup

Propane fuel only (exterior mount)

Diagnostic Interface

The onboard LED display shows maintenance reminders and error codes directly on the unit to streamline servicing without specialized tools.

Pros & cons43

Pros

• High 199,000 BTU output provides up to 9.8 GPM to handle demanding household fixtures
• Outdoor installation bypasses indoor vent pipe routing through roofs or walls
• Built-in LED screen alerts users with diagnostic error codes and service reminders
• Comprehensive residential warranty coverage includes 1-year labor alongside parts

Cons

• Requires a dedicated exterior liquid propane supply rather than natural gas
• WiFi monitoring is not integrated and requires purchasing the separate Controlr module
• At 52.8 pounds, it is heavier to position than lower-output outdoor models

3

Rheem RTG-84DVLP-3 High Efficiency Non-Condensing Indoor Tankless Liquid Propane Water

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  9.6
• Brand
  Rheem

Key specs2

Indoor Exhaust Setup

Direct-vent piping required

Propane Flow Capacity

Produces 180,000 BTU/hr to supply up to 8.4 GPM for propane-powered homes needing multiple indoor fixture feeds.

Pros & cons43

Pros

• Indoor direct-vent configuration allows secure installation inside utility spaces
• Provides 8.4 GPM at 35-degree rise to serve 3 to 4 simultaneous hot water points
• Direct-dial digital control panel enables precise 1-degree temperature regulation
• Wall-mounted compact cabinet frees up valuable basement or closet floor area

Cons

• Requires dedicated direct-vent exhaust ductwork routed through an exterior wall or roof
• Non-condensing 0.82 UEF does not match the 0.97 efficiency of condensing alternatives
• Configured strictly for liquid propane connections and lacks integrated WiFi controls

4

Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water

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  9.3
• Brand
  Rheem

Key specs2

Outdoor Wall Clearance

Exterior wall mount (no flue pipe)

Mid-Size Water Delivery

Generates 160,000 BTU/hr on natural gas to deliver 7.0 GPM, well-matched for 2 to 3 shower bathrooms without running indoor flues.

Pros & cons43

Pros

• Eliminates vent pipe purchases and interior wall penetrations via outdoor mounting
• Supplies 7.0 GPM at 35-degree rise to comfortably run 2 to 3 showers simultaneously
• Lightweight 39.25-pound metal enclosure facilitates exterior wall bracket mounting
• Built-in freeze protection system helps safeguard internal components from cold air

Cons

• Limited to 160,000 BTU, delivering less peak volume than larger 180,000 BTU heaters
• Outdoor installation is restricted to exterior walls with accessible gas plumbing
• Remote smartphone operation is unsupported because the unit lacks WiFi capability

5

Rinnai RE160eP Non-Condensing Propane Tankless Water Heater

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  9.0
• Brand
  Rinnai

Key specs2

Propane Fixture Output

Up to 6.1 GPM (up to 5 fixtures)

Cabinet Footprint

Measures 10.77 by 14.05 by 24.64 inches, fitting compact exterior wall spaces where indoor venting is unfeasible.

Pros & cons43

Pros

• Outdoor propane setup saves interior utility room space with zero indoor venting
• Capable of delivering up to 6.1 GPM to service up to 5 household fixtures at once
• LED display panel gives clear service reminders and troubleshooting error codes
• Compact suitcase-sized cabinet mounts neatly on exterior siding or masonry

Cons

• Maximum flow rate is lower than larger RE-series models when incoming water is cold
• Does not include wireless app controls without purchasing the extra Controlr accessory
• Requires outdoor propane tank access and cannot be converted to indoor operation

6

Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water

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  8.9
• Brand
  Rheem

Key specs2

Internal Leak Detection

LeakGuard detection integrated

Indoor Direct Venting

Engineered for indoor wall mounting with a direct-vent pipe connection, paired with automated leak sensors for basement installations.

Pros & cons43

Pros

• Built-in LeakGuard detection senses internal water leaks to avoid utility room damage
• Direct-vent indoor installation protects the unit inside conditioned spaces
• Supplies 7.0 GPM at 35-degree rise to keep 2 to 3 showers running concurrently
• Precision digital LED controls allow water temperature setting changes by 1 degree

Cons

• Requires cutting vent pathways through the building envelope for direct venting
• Non-condensing 0.82 UEF uses more fuel per gallon than 0.97 UEF condensing heaters
• Operates solely on natural gas and cannot connect directly to propane lines

7

Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water

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  8.7
• Brand
  Rheem

Key specs2

Liquid Propane Outdoor Mounting

Outdoor LP setup (zero vent pipe)

Freeze Safety System

Equipped with built-in freeze protection and flame failure safeguards to maintain outdoor propane operation through cold snaps.

Pros & cons43

Pros

• Exterior propane installation removes the need for indoor venting materials and labor
• Delivers 7.0 GPM at a 35-degree rise for continuous operation across 2 to 3 showers
• Durable gray metal cabinet incorporates freeze protection for winter conditions
• Compact 39.25-pound structure allows straightforward exterior wall bracket mounting

Cons

• Propane-specific fuel assembly cannot be connected to residential natural gas mains
• Flow capacity of 7.0 GPM may drop in cold climates with freezing groundwater temps
• Lacks smart device integration and does not include wireless network hardware

8

Rinnai RE180iN Non-Condensing Natural Gas Tankless Water Heater, Up to

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  8.5
• Brand
  Rinnai

Key specs2

Indoor Natural Gas Venting

Indoor direct venting needed

Maintenance Alerts

Built-in LED diagnostic panel provides active service reminders and error codes to simplify ongoing maintenance schedules.

Pros & cons43

Pros

• High 180,000 BTU natural gas burner delivers up to 8.5 GPM for multi-bath residences
• Indoor wall mounting keeps the heater safe from outdoor elements and freezing temps
• Front LED display surfaces error codes and maintenance reminders for rapid diagnosis
• Robust residential warranty includes 15 years on heat exchanger plus 1-year labor

Cons

• Requires dedicated non-condensing indoor venting runs that add to installation costs
• Weighs 54 pounds, requiring sturdy wall framing support during indoor placement
• WiFi monitoring requires buying and configuring the separate Controlr module

9

NEW Rinnai RX130iN Condensing Smart Sense Natural Gas or Propane

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  8.1
• Brand
  Rinnai

Key specs3

Condensing Efficiency Rating

0.97 UEF ultra-high efficiency

Fuel Flexibility

Smart Sense gas control works with either natural gas or propane, eliminating fuel lock-in during plumbing upgrades.

Dual-Location Venting

Versa Vent design installs indoors or outdoors, though outdoor placement requires the RX-OVC vent cap accessory.

Pros & cons43

Pros

• High 0.97 UEF condensing efficiency extracts maximum heat to reduce energy waste
• Versa Vent technology allows flexible installation either indoors or outdoors
• Smart Sense gas control system accommodates either natural gas or propane supplies
• Integrated Quick Flush feature simplifies routine descaling and maintenance tasks

Cons

• Indoor condensing setup requires running a dedicated condensation drain line
• Outdoor installation requires purchasing the separate RX-OVC vent cap accessory
• Maximum heating power is capped at 130,000 BTU, lower than 180k-199k non-condensing units

10

Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater

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  7.8
• Brand
  Rinnai

Key specs2

High-Demand Outdoor Output

Up to 9.8 GPM (6 fixtures)

Exterior Casing Design

Suitcase-sized 10.77 by 14.05 by 24.64 inch enclosure mounts outdoors, eliminating the labor and expense of indoor exhaust ducts.

Pros & cons43

Pros

• Capable of up to 9.8 GPM to handle up to 6 simultaneous fixtures without pressure loss
• Outdoor natural gas design avoids cutting vent exhausts through house framing
• LED display panel offers straightforward maintenance alerts and fault diagnosis
• Heavy-duty construction backed by a 15-year residential heat exchanger warranty

Cons

• Outdoor location exposes the chassis to ambient temperatures and weather elements
• Requires connection to a natural gas line and cannot run on standard propane tanks
• Separate Controlr accessory must be purchased if WiFi monitoring is desired

11

Rinnai RE199iN Non-Condensing Natural Gas Tankless Water Heater, Up to

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  7.3
• Brand
  Rinnai

Key specs2

Peak Indoor Capacity

199,000 BTU natural gas

Indoor Space Requirements

Requires adequate wall space and proper dedicated non-condensing venting for indoor operation, servicing up to 9.8 GPM.

Pros & cons43

Pros

• Powerful 199,000 BTU burner supplies up to 9.8 GPM for large, multi-shower homes
• Indoor installation safeguards the unit against freezing winter temperatures
• Digital LED display provides rapid diagnostic codes to simplify servicing tasks
• Compact wall-hung layout replaces bulky storage tanks to open up utility room space

Cons

• Requires high-temperature metal venting through walls or roofs to vent exhaust safely
• Non-condensing technology does not achieve the 0.97 UEF rating of condensing models
• Requires professional installation and venting setup that adds to upfront labor costs

Last update on 2026-10-16 / Affiliate links / Images, Product Titles, and Product Highlights from Amazon Product Advertising API

Does a condensing tankless water heater save enough energy to justify your installation layout?

It depends on your plumbing access and exhaust pathways. Non-condensing gas heaters listed with a 0.82 Uniform Energy Factor (UEF) reduce energy costs by up to 34% compared to 50-gallon electric tank heaters. Condensing options like the Rinnai RX130iN extract extra heat from exhaust at 130,000 BTU, but the process creates acidic condensate that requires a dedicated drainage route. If your utility space lacks a nearby floor drain, adding custom plumbing lines can wipe out immediate operating savings.

Do you need a drain line for a condensing water heater?

Yes, condensing units require a drainage exit for moisture created during secondary heat recovery. When hot exhaust cools inside the heat exchanger, condensation forms and must drain safely away from the appliance. Non-condensing models like the Rheem RTG-70DVLN-3 or Rinnai RE199iN vent hotter exhaust directly outdoors, so they operate without any condensate drain line. If you select a condensing heater for a space without a gravity drain, verify whether an auxiliary pump is required to clear runoff.

Can you install an outdoor tankless water heater to avoid cutting vent holes?

Yes, mounting an outdoor tankless unit eliminates indoor exhaust ducting and roof penetrations. Outdoor heaters like the Rheem RTG-84XLN-3 and the Rinnai RE199eP mount on an exterior wall and exhaust directly into open air. This avoids the cost of running specialized venting through living spaces or attics. Certain models, like the Rinnai RX130iN, include a Versa Vent system that allows outdoor mounting while supporting either natural gas or propane supplies.

What flow rate in gallons per minute do you need for household fixtures?

Flow demands typically range from 7.0 to 9.8 GPM depending on how many fixtures you run at the same time. A 160,000 BTU unit such as the Rheem RTG-70XLN-3 supplies 7.0 GPM at a 35°F temperature rise, which supports standard single-point or moderate usage. Larger 199,000 BTU units like the Rinnai RE199iN deliver up to 9.8 GPM to supply multiple fixtures at once. If your home has strict fuel limits or electrical preferences, explore tankless systems matched to home electrical panels before making plumbing changes.

Can a tankless water heater run on both propane and natural gas?

Most tankless models are built for a single fuel source and cannot switch without specific internal hardware. Units like the Rheem RTG-84DVLP-3 run strictly on liquid propane, while the Rinnai RE180iN requires natural gas. An exception is the Rinnai RX130iN, which uses Smart Sense technology to function with either natural gas or propane. If you must use bottled fuel, check out dedicated propane heaters with safe venting to confirm fuel inlet specs before purchasing.

How do indoor venting requirements differ between condensing and non-condensing models?

Non-condensing indoor heaters produce high-temperature exhaust that requires dedicated direct-vent materials, while condensing heaters release cooler exhaust. Indoor non-condensing heaters like the Rheem RTG-70DVLN-3 and Rheem RTG-84DVLP-3 use direct venting to push high-heat exhaust directly outside. Condensing models cool the exhaust significantly during secondary heating, allowing versatile configurations like the Versa Vent on the Rinnai RX130iN for indoor venting. Always check your wall clearance and pipe diameter specifications in the product manual before cutting vent openings.