11 Condensing Vs Non Condensing Tankless Heater of 2026 To Avoid Costly Venting

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

Zero indoor venting needed (outdoor wall mount)

Simultaneous Fixture Capacity

Delivering 180,000 BTU/hr and 8.4 GPM at a 35-degree rise, this unit supports 3 to 4 simultaneous showers without temperature drops.

Pros & cons53

Pros

• Outdoor wall-mount design eliminates the need for indoor exhaust venting runs
• High 180,000 BTU/hr output provides 8.4 GPM to support 3 to 4 simultaneous showers
• Digital LED control panel allows temperature adjustments in exact 1-degree increments
• Built-in freeze protection and durable metal cabinet protect exterior components
• Long 15-year heat exchanger warranty paired with 5-year parts coverage

Cons

• Outdoor-only installation makes it unsuitable for homes without exterior mounting space
• Requires dedicated natural gas line supply and cannot run on liquid propane
• Lacks integrated wireless connectivity for remote phone monitoring

2

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

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  9.6
• Brand
  Rheem

Key specs2

Direct Vent Configuration

Indoor direct vent with dual-pipe exhaust

Propane Demand Capacity

Provides 180,000 BTU/hr output for homes running off liquid propane, maintaining 8.4 GPM for up to 4 concurrent showers.

Pros & cons53

Pros

• Delivers 8.4 GPM at a 35-degree rise to supply 3 to 4 simultaneous showers indoors
• 0.82 Uniform Energy Factor eliminates the need for dedicated condensate drainage
• Compact wall-mount design frees up valuable utility room floor space
• Multi-point safety system includes built-in flame failure and freeze protection
• Backed by a 15-year heat exchanger warranty and 5-year parts warranty

Cons

• Indoor direct-vent system requires installing dedicated intake and exhaust piping
• Configured strictly for liquid propane and cannot connect directly to natural gas
• Heavier indoor footprint at 46.5 pounds compared to outdoor Rheem models

3

Rheem RTG-70DVLP-3 High Efficiency Non-Condensing Indoor Tankless Liquid Propane Water

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  9.5
• Brand
  Rheem

Key specs2

Indoor Venting Layout

Uses an indoor direct vent design to draw outside air and vent combustion gases directly through an exterior wall.

Household Demand Sizing

160,000 BTU/hr supports 2 to 3 showers

Pros & cons53

Pros

• Supplies 7.0 GPM at 35-degree rise to easily run 2 to 3 showers simultaneously
• Non-condensing 0.82 UEF rating requires no condensate drain line installation
• Precise digital LED display adjusts water temperature in 1-degree increments
• Includes mounting hardware and comprehensive manual for straightforward setup
• CSA certified with integrated freeze and flame-failure safety systems

Cons

• Indoor direct vent installation requires exterior wall penetrations for venting
• Sized for 160,000 BTU/hr, offering less peak flow than 8.4 GPM alternatives
• Liquid propane connection requires an on-site tank rather than utility gas lines

4

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

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  9.3
• Brand
  Rheem

Key specs2

Exterior Wall Placement

Outdoor wall mount with metal cabinet

Moderate Flow Output

Supplies 7.0 GPM at a 35-degree rise on natural gas, matching the daily hot water demands of 2 to 3 simultaneous fixtures.

Pros & cons53

Pros

• Outdoor installation bypasses indoor vent pipe routing and roof cutting completely
• Generates 160,000 BTU/hr to deliver 7.0 GPM for 2 to 3 concurrent showers
• Rugged metal cabinet features integrated freeze protection for outdoor longevity
• Digital LED controller provides precise 1-degree temperature setting adjustments
• Covered by a 15-year heat exchanger warranty and 5-year parts warranty

Cons

• Cannot be mounted indoors or in enclosed areas lacking outdoor ventilation
• Delivers lower peak flow than 180,000 BTU models during heavy winter demand
• Natural gas dedicated design is incompatible with liquid propane systems

5

Rinnai RE140iN Non-Condensing Natural Gas Tankless Water Heater

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  9.2
• Brand
  Rinnai

Key specs2

Service Code Monitoring

The front LED screen displays active service reminders and clear error codes to simplify maintenance troubleshooting.

Compact Cabinet Footprint

10.77 x 14.05 x 27.28 inches (50.75 lb)

Pros & cons53

Pros

• Compact suitcase-sized cabinet measures only 10.77 by 14.05 by 27.28 inches
• Built-in LED screen displays clear diagnostic error codes and service reminders
• Delivers up to 5.3 GPM to supply hot water for up to 5 fixtures at once
• Improved internal layout simplifies maintenance and speeds up routine servicing
• Backed by 15-year heat exchanger, 5-year labor, and 1-year parts guarantees

Cons

• Listing contains conflicting indoor and outdoor placement notes that require verification
• Controlr WiFi module is sold separately for smart home network connectivity
• Peak flow of 5.3 GPM may drop significantly in regions with cold ground water

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 Water Monitoring

Built-in LeakGuard detects internal leaks

Indoor Natural Gas Supply

Designed for direct-vent indoor installation on natural gas lines, providing 160,000 BTU/hr across 2 to 3 showers.

Pros & cons53

Pros

• Integrated LeakGuard detection monitors for internal leaks to prevent water damage
• 160,000 BTU/hr output provides 7.0 GPM to serve 2 to 3 simultaneous showers
• Non-condensing operation avoids the extra labor of plumbing a condensate drain
• Digital LED screen provides precision control within 1 degree of target temperature
• CSA certified unit includes multi-point flame failure and freeze safeguards

Cons

• Indoor direct venting requires running dedicated intake and exhaust flues outside
• Limited to natural gas supply lines and cannot run on propane fuel sources
• Does not include wireless network capabilities for remote phone control

7

Rinnai RE140iP Non-Condensing Propane Tankless Water Heater, Up to 5.3

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  8.8
• Brand
  Rinnai

Key specs2

Diagnostic Display

LED screen tracks service and error codes

Propane Heating Rate

A 140,000 BTU burner supplies up to 5.3 GPM across up to 5 connected fixtures simultaneously on liquid propane.

Pros & cons53

Pros

• Delivers up to 5.3 GPM to power up to 5 household fixtures simultaneously
• Onboard LED display delivers active maintenance reminders and error code readouts
• 140,000 BTU burner is optimized for dedicated liquid propane residential hookups
• Compact wall-hung footprint fits easily into tight indoor closets or basements
• Includes 15-year heat exchanger, 5-year labor, and 1-year parts coverage

Cons

• Indoor installation requires proper direct-vent flue pipe routing through walls
• WiFi control module must be purchased separately if app monitoring is desired
• Lower 140,000 BTU rating produces less flow during extreme cold incoming water conditions

8

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

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  8.7
• Brand
  Rheem

Key specs2

Zero Flue Installation

Outdoor installation eliminates venting

Propane Output Sizing

The 160,000 BTU/hr liquid propane burner supplies 7.0 GPM at a 35-degree rise for 2 to 3 simultaneous showers.

Pros & cons53

Pros

• Outdoor wall-hung design avoids all indoor venting ductwork and wall penetrations
• Produces 160,000 BTU/hr to supply 7.0 GPM across 2 to 3 simultaneous showers
• Durable exterior metal cabinet features built-in electrical freeze protection
• Digital LED panel allows temperature calibration in 1-degree increments
• 0.82 UEF rating eliminates the need to route acidic condensate drain lines

Cons

• Outdoor-only installation makes it impractical for spaces without exterior clearance
• Requires access to a liquid propane tank and line rather than natural utility gas
• Missing smart home connectivity for smartphone status tracking

9

Rheem RTG-84DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water

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  8.7
• Brand
  Rheem

Key specs2

Indoor High-Flow Natural Gas

180,000 BTU/hr provides 8.4 GPM indoors

Precision Temperature Control

Digital LED panel allows exact water temperature adjustments in 1-degree increments for consistent whole-home output.

Pros & cons53

Pros

• High 180,000 BTU/hr capacity delivers 8.4 GPM to support 3 to 4 simultaneous showers
• Non-condensing design saves up to 34% energy over standard 50-gallon electric tanks
• Direct vent indoor mounting frees up basement floor space with clean wall hanging
• Digital LED controller maintains steady hot water with 1-degree adjustments
• Robust 15-year heat exchanger and 5-year parts residential manufacturer warranty

Cons

• Indoor setup requires specialized direct-vent intake and exhaust flue routing
• Unusable on liquid propane supply setups without dedicated conversion hardware
• Listing does not include the built-in LeakGuard shutoff found on select 7.0 models

10

Rheem High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water Heater,

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  8.6
• Brand
  Rheem

Key specs2

Outdoor Propane Setup

Exterior wall mount eliminates indoor flue

High-Volume Capacity

Delivers 180,000 BTU/hr and 8.4 GPM on liquid propane to handle 3 to 4 simultaneous showers in multi-bath homes.

Pros & cons53

Pros

• High-capacity 180,000 BTU/hr rating supplies 8.4 GPM for 3 to 4 concurrent showers
• Outdoor installation completely eliminates expensive interior venting duct runs
• Operates at 0.82 UEF without producing acidic condensate that requires a drain line
• Built-in freeze protection and durable cabinet protect unit in outdoor conditions
• Backed by a 15-year heat exchanger warranty and 5-year parts warranty

Cons

• Outdoor mounting requires suitable exterior wall space and exterior gas line routing
• Restricted to liquid propane fuel sources and cannot operate on utility natural gas
• Remote app connectivity is not supported on this non-WiFi model

11

Rinnai RE180eP Non-Condensing Propane Tankless Water Heater

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  7.8
• Brand
  Rinnai

Key specs2

Outdoor Fixture Delivery

Up to 6.9 GPM across 5 fixtures at once

Labor Warranty Coverage

Comes with a 5-year labor guarantee alongside 15-year heat exchanger and 1-year parts coverage for residential use.

Pros & cons53

Pros

• Outdoor propane design eliminates the cost and labor of indoor chimney venting
• High output provides up to 6.9 GPM across 5 fixtures at once for large households
• Clean internal component layout speeds up routine maintenance and inspections
• Built-in digital LED display delivers diagnostic error codes and service reminders
• Comprehensive residential warranty provides 15 years on heat exchanger and 5 on labor

Cons

• Smart home wireless management requires purchasing an optional Controlr module
• Listing specs note 8.5 GPM size while features state 6.9 GPM, requiring flow verification
• Dedicated outdoor propane configuration is not compatible with natural gas piping

Last update on 2026-10-17 / Affiliate links / Images, Product Titles, and Product Highlights from Amazon Product Advertising API

What is the main difference between condensing and non-condensing tankless water heaters?

The primary difference lies in how each system handles exhaust heat and drainage. Non-condensing tankless water heaters operate at a 0.82 Uniform Energy Factor (UEF) and discharge hot exhaust gases directly through the vent pipe, which prevents acidic condensation from forming inside the unit. Condensing models extract extra heat from exhaust gases, creating an acidic liquid byproduct that requires a dedicated drainage line and an acid neutralizer. If you want to bypass venting requirements entirely, you can evaluate an electric tankless water heater for home use to weigh electrical panel capacity against gas flue modifications.

Can an outdoor non-condensing tankless heater eliminate venting work?

Yes, mounting a non-condensing water heater outdoors completely removes the need for indoor venting pipes and roof penetrations. Units such as the Rheem RTG-84XLN-3 and RTG-70XLN-3 are engineered specifically for exterior wall placement, venting exhaust air straight into the open atmosphere from the cabinet. Choosing an outdoor setup prevents expensive structural cutting through exterior walls or attics. You only need to verify that exterior clearances and pipe freeze protection match your local climate and building codes.

Is a 7.0 GPM or 8.4 GPM flow rate necessary for multi-bathroom homes?

An 8.4 GPM flow rate is generally necessary if your household runs multiple hot water fixtures at the same time. At a 35°F temperature rise, an 8.4 GPM model delivers 180,000 BTU/hr of heating capacity, while a 7.0 GPM unit produces 160,000 BTU/hr under the same temperature rise. If two showers and a washing machine run concurrently, the higher capacity prevents sudden flow restrictions. For smaller households with lower simultaneous demand, compact units like the Rinnai RE140iP supply up to 5.3 GPM at 140,000 BTU to handle single-fixture use comfortably.

Do non-condensing tankless heaters require a condensate drain line?

No, non-condensing gas tankless water heaters do not need a condensate drain line. Because models like the Rheem RTG-70DVLN-3 maintain a 0.82 UEF rating, the flue gas temperature stays high enough to exit without condensing into moisture. This design eliminates the need to route plastic drain tubes, punch holes for drain lines, or set up neutralizing filters near the floor. It simplifies retrofit installations in basements or closets where a floor drain is not readily accessible.

How do natural gas and liquid propane connections differ on these heaters?

Tankless heaters are engineered around specific fuel types and cannot switch between fuels without dedicated manufacturer conversion parts. Natural gas models like the Rheem RTG-84DVLN-3 connect to residential utility gas lines, whereas liquid propane units like the Rheem RTG-84DVLP-3 run on dedicated propane tanks. If your property relies on bottled fuel, reviewing guidelines for a propane heater for home setup will clarify fuel delivery and safety clearances. Check the fuel specification on the product rating plate before purchasing to prevent dangerous burner mismatches.

What wall dimensions and clearances are required for an indoor non-condensing heater?

Indoor non-condensing units require a relatively small wall footprint but need adequate clearance for plumbing and vent collars. Standard Rheem direct-vent indoor units measure 10.27 inches deep, 13.5 inches wide, and 24.2 inches high, weighing 46.5 pounds. Compact alternatives such as the Rinnai RE140iN measure 10.77 by 14.05 by 27.28 inches, offering an enclosure comparable to a small suitcase. Confirm the required side and top clearances in the product manual before mounting to ensure unobstructed access for maintenance and pipe connections.