When searching for the best tankless gas water heater condensing models, the focus often falls on efficiency, capacity, and installation versatility. The Rinnai RX199iN stands out as the overall top pick thanks to its high flow rate and advanced features. For those on a budget, the Westinghouse offers solid performance at a lower price point, though with slightly lower capacity. Meanwhile, the Rheem RTG-70DVLN-3 is a non-condensing option that appeals to buyers prioritizing straightforward installation. Each of these models presents distinct tradeoffs—whether it’s upfront cost, capacity, or features—that influence the best choice for different needs. Continue reading for a detailed breakdown of these options and more to help you find the perfect fit for your home.
Key Takeaways
- High flow rate models like Rinnai RX199iN deliver the best performance for large households, but come at a premium price.
- Condensing technology significantly boosts efficiency, making models like Rheem and Rinnai top choices for long-term savings.
- Installation flexibility varies; indoor units often require venting and space considerations, while outdoor units offer easier setup.
- WiFi and remote control features are increasingly common, adding convenience but often increasing upfront costs.
- Choosing between condensing and non-condensing models depends on budget and desired efficiency levels—condensing units generally cost more initially but save more over time.
More Details on Our Top Picks
Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Heater 7.0 GPM, 160,000 BTUs
This Rheem model stands out for its proven durability, straightforward installation, and reliable performance in typical household scenarios. Compared with the ThermoMate CZ480NG, it offers a slightly higher flow rate, making it suitable for homes with multiple bathrooms. Its non-condensing design means it’s simpler but less efficient—yet more cost-effective upfront. The Hot Start Programming prevents cold bursts, a key feature for back-to-back showers. While its efficiency (0.82) isn’t as high as condensing units, it compensates with a long track record of dependable operation. The compact, wall-mounted design makes it ideal for small indoor spaces but limits capacity for larger households. The main tradeoff involves lower efficiency and no condensate neutralization, requiring more attention to venting and maintenance. Overall, this model suits buyers seeking a balance of reliability and ease of installation without the complexity of condensing technology.
Pros:- Proven durability with a long-lasting build
- Easy wall mounting suitable for small spaces
- Reliable hot water supply with Hot Start Programming
Cons:- Lower efficiency (0.82 UEF) compared to condensing units
- No condensate neutralizer, requiring proper venting
Best for: Homeowners needing a dependable indoor unit for 2-3 bathroom homes with moderate hot water demand.
Not ideal for: Large households or those prioritizing maximum energy efficiency, since it lacks condensing features.
- Flow Rate:7 GPM
- BTUs:160,000
- Efficiency:0.82
- Wattage:132 watts
- Voltage:120V
- Mount Type:Wall
Bottom line: This model is perfect for buyers who want a straightforward, reliable indoor tankless heater with proven performance and easy installation.
ThermoMate CZ480NG 5.28GPM Condensing Tankless Water Heater, 0.86 UEF High Efficiency Instant On-Demand Hot Water
This ThermoMate model makes a compelling case for energy savings, boasting a 0.86 UEF and dual heat exchangers that maximize heat recovery. It supplies up to 5.28 GPM, which is slightly less than the Rinnai RX130iN but still sufficient for two simultaneous showers. Its condensing design produces mildly acidic condensate requiring a neutralizer, adding a small installation consideration. Compared to the Rinnai RX130iN, it offers comparable efficiency at a lower price point, making it attractive for budget-conscious buyers seeking condensing technology. Its stainless steel and oxygen-free copper heat exchangers enable better durability and heat transfer. The built-in water flow sensor adjusts heating 20,000 times per second, maintaining water temp within ±1°F for user comfort. The main tradeoff is a slightly lower flow rate and the need for condensate neutralization, but it offers excellent energy savings and long-term operational cost reduction. It’s ideal for users prioritizing efficiency without sacrificing performance.
Pros:- High efficiency (0.86 UEF) with dual heat exchangers
- Cost-effective compared to similar condensing units
- Adjusts water temperature precisely with advanced sensors
Cons:- Requires installation of an external condensate neutralizer
- Flow rate slightly lower than some 5+ GPM models
Best for: Energy-conscious households seeking high efficiency with moderate flow needs and willingness to handle condensate neutralization.
Not ideal for: Large families with high simultaneous hot water demand or those unwilling to install condensate treatment systems.
- Flow Rate:5.28 GPM
- BTUs:114,000
- Efficiency:0.86 UEF
- Dimensions:21″H x 13″W x 7″D
- Maximum Temperature:140°F
- Material:Stainless Steel & Copper
Bottom line: This condensing model offers excellent value for those wanting high efficiency and long-term savings in a compact design.
APUS 190,000 BTU Outdoor Tankless Water Heater, 8.1 GPM Natural Gas Instant Hot Water with WiFi & Remote Control
The APUS 8.1 GPM outdoor heater excels in providing high-capacity hot water for large households or commercial use, especially in harsh climates. Its 190,000 BTU output supports multiple outlets simultaneously, making it ideal for outdoor installations where space is limited and durability matters. Compared to indoor models like the Rheem RTG-70DVLN-3, it offers a higher flow rate and outdoor versatility, featuring wind-resistant construction and frost protection. The WiFi and remote control functions allow for easy adjustments and diagnostics from afar, adding modern convenience. Its oxygen-free copper heat exchanger enhances durability and heat transfer efficiency. The main tradeoff involves its outdoor placement, which exposes it to weather elements, and the need for proper venting and protection. It’s perfect for outdoor setups requiring high volume and remote monitoring but less suitable for indoor or small-space applications.
Pros:- High capacity with 8.1 GPM flow rate
- WiFi and remote control for convenience
- Durable outdoor construction with frost protection
Cons:- Requires outdoor installation with weatherproofing
- Higher upfront cost and complexity
Best for: Large outdoor spaces or remote locations needing high flow and remote management.
Not ideal for: Indoor installations or households with low hot water demand, due to its size and outdoor requirements.
- Flow Rate:8.1 GPM
- BTUs:190,000
- Maximum Temperature:140°F
- Material:Oxygen-free Copper
- Power Source:Natural Gas
- Dimensions:22.48″H x 15.51″W x 6.54″D
Bottom line: This outdoor heater is best suited for large households or outdoor applications demanding high flow and remote control capabilities.
NEW Rinnai RX130iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater, Indoor or Outdoor, Up to 7.1 GPM, 130,000 BTU
This Rinnai model offers exceptional versatility, capable of indoor or outdoor installation thanks to Versa Vent, and supports both natural gas and propane. Its 7.1 GPM flow rate makes it suitable for larger households with multiple fixtures, and the high efficiency (UEF .97) ensures low operational costs. Compared with the Rheem RTGH-90DVLN-3, it provides similar high efficiency but with added flexibility for outdoor use and smart home compatibility via WiFi (via optional module). Its compact size and advanced features, including Quick Flush and a digital interface, make maintenance and operation straightforward. The main consideration is the need for professional installation and optional WiFi module purchase. This model is ideal for buyers wanting a highly adaptable, efficient, and remotely manageable system that can be installed virtually anywhere.
Pros:- Supports indoor and outdoor installation
- High efficiency (UEF .97) with condensing technology
- Supports both natural gas and propane
Cons:- WiFi control is optional and sold separately
- Requires professional installation
Best for: Large households wanting flexibility, smart controls, and indoor/outdoor installation options.
Not ideal for: Budget-conscious buyers or those unwilling to handle professional installation and optional WiFi upgrades.
- Flow Rate:7.1 GPM
- BTUs:130,000
- Efficiency:0.97 UEF
- Maximum Temperature:140°F
- Power Source:Natural Gas or Propane
- Dimensions:17-11/16″W x 23.7″H
Bottom line: This model is perfect for tech-savvy buyers seeking maximum flexibility, smart features, and high efficiency in a compact design.
Rheem RTGH-90DVLN-3 Super High Efficiency Indoor Tankless Gas Water Heater, 9 GPM, 180,000 BTUs
This Rheem unit stands out for its impressive 9 GPM flow rate and high BTU output, making it suitable for large families or demanding applications. Its condensing design achieves a high efficiency (0.93 UEF), reducing energy costs over time. Compared to the APUS 8.1 GPM Outdoor, it excels indoors with a more robust capacity, perfect for simultaneous multiple outlets. The Hot Start Programming ensures consistent hot water without cold bursts, while the overheat protection adds safety. Its stainless steel construction ensures durability, and the compact wall-mount saves space. The main tradeoff involves its indoor-only installation and higher initial cost. This heater is ideal for those needing large volume output in a reliable, indoor format but less suited for outdoor use or smaller households.
Pros:- High flow rate of 9 GPM for large households
- Excellent reliability with high BTU output
- Efficient condensing technology
Cons:- Indoor installation required, limiting outdoor use
- Higher upfront investment compared to lower capacity models
Best for: Large households needing reliable, high-flow indoor hot water all day long.
Not ideal for: Small homes or outdoor applications due to its indoor-only design and size.
- Flow Rate:9 GPM
- BTUs:180,000
- Efficiency:0.93
- Maximum Temperature:140°F
- Wattage:132W
- Mount Type:Wall
Bottom line: This high-capacity indoor model is best for large families demanding continuous hot water with high reliability.
Westinghouse Natural Gas Tankless Water Heater, Indoor Installation, Max 5.1 GPM 120,000 BTU, WIFI Enable Temp Self Modulating Non Condensing High Efficiency for Whole Home, APOLO Performance
This Westinghouse model stands out for its WiFi-enabled temperature control and self-modulating technology, which allows for precise water temperature management and remote adjustments. Compared to the Rinnai RX160iN, it offers more advanced app connectivity, making it ideal for tech-savvy homeowners seeking convenience. However, its flow rate of 5.1 GPM is lower, limiting simultaneous usage compared to larger-capacity options. The unit’s indoor-only design ensures safety and space efficiency but means it’s unsuitable for outdoor installations or high-demand households. The high efficiency and safety certifications provide peace of mind, while the 2-year full warranty and 5-year heat exchanger coverage add durability. This pick makes the most sense for users prioritizing smart features and indoor installation, especially in smaller households where moderate flow is sufficient.
Pros:- WiFi-enabled remote temperature control
- Effortless self-modulating operation for energy savings
- Compact and suitable for indoor installation
Cons:- Limited flow rate of 5.1 GPM, restricting simultaneous fixtures
- Indoor-only design limits outdoor or high-demand use
Best for: Homeowners seeking a compact, WiFi-enabled indoor water heater with precise temperature control
Not ideal for: Large families with high simultaneous hot water needs or outdoor installation requirements
- Flow Rate:5.1 GPM
- BTU:120,000
- Efficiency:Non condensing
- Installation:Indoor
- WiFi Enabled:Yes
- Warranty:2 years full, 5 years heat exchanger
Bottom line: Best suited for tech-savvy users who need an efficient, indoor, smart water heater for moderate household use.
ThermoMate CZ422NG Natural Gas Tankless Water Heater, Up to 5 GPM 113,000 BTU, High Efficiency Instant On-Demand Hot Water for Whole House Use, Indoor Residential Water Heater with Multi-Point Heating
This ThermoMate model is a solid choice for those new to tankless water heaters, offering straightforward operation and a good balance of capacity at 5 GPM, comparable to the Westinghouse. It’s designed for indoor use, making installation simple for typical residential settings, and its high thermal efficiency of 98% helps reduce energy costs. Compared to the Rinnai RX199iN, it lacks WiFi connectivity but compensates with a lower price point and ease of setup. The unit’s multiple safety protections and durable copper heat exchanger increase reliability, though its flow rate limits simultaneous fixtures to a couple of showers. The built-in LED touchscreen simplifies adjustments and monitoring, making it ideal for users who want a user-friendly experience without extra smart features. This makes it a practical choice for small households or those testing tankless technology for the first time.
Pros:- Easy-to-use LED touchscreen display
- High efficiency at 98% thermal efficiency
- Reliable safety protections and durable copper heat exchanger
Cons:- Lacks WiFi control or smart features
- Flow rate of 5 GPM may limit simultaneous fixtures
Best for: First-time tankless water heater buyers or budget-conscious homeowners needing reliable indoor hot water
Not ideal for: Large households or users wanting smart home integration and high flow capacity
- Flow Rate:5 GPM
- BTU:113,000
- Efficiency:98%
- Installation:Indoor
- Display:LED touchscreen
- Safety Features:Multiple protections
Bottom line: Ideal for beginners or small households seeking a straightforward, efficient indoor water heater without smart features.
NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater, Indoor or Outdoor Water Heater, Up to 11.1 GPM, 199,000 BTU
This Rinnai RX199iN excels in delivering high hot water flow at 11.1 GPM, making it suitable for larger households or busy families. Its high BTU output of 199,000 ensures rapid heating and ample hot water supply, surpassing the capacity of the Westinghouse and ThermoMate models. Its flexible installation options—indoor or outdoor—set it apart from indoor-only units, providing versatility for various home layouts. The unit’s condensing technology achieves a UEF of .98, maximizing energy efficiency, while WiFi control (via optional module) adds convenience for tech-savvy users. However, its size and complexity suggest a need for professional installation, and its higher price reflects its premium capacity and features. If your household requires consistent, large-volume hot water with outdoor install capability, this model is a compelling choice.
Pros:- High flow rate of 11.1 GPM for multiple fixtures
- Indoor and outdoor installation options
- Ultra-high energy efficiency with UEF .98
Cons:- Higher cost and complexity of installation
- Heavier and larger, requiring professional setup
Best for: Large households needing high flow rates and outdoor install flexibility
Not ideal for: Small households or users with limited space seeking budget options
- Flow Rate:11.1 GPM
- BTU:199,000
- Efficiency:UEF .98
- Installation:Indoor/outdoor
- Max Temperature:140°F
- Power Source:Natural Gas or Propane
Bottom line: Best suited for large households or outdoor installation needs that demand high capacity and efficiency.
NEW Rinnai RX160iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater, Indoor or Outdoor Water Heater, Up to 9 GPM, 160,000 BTU
This Rinnai RX160iN offers a balanced capacity of 9 GPM, making it suitable for medium-sized households. Its versatility in installation—indoor or outdoor—matches the RX199iN, but with slightly lower capacity and BTU output at 160,000. The high efficiency of UEF .97 and smart features, including WiFi compatibility with the Control-R module, provide convenience and cost savings. Its compact size and ease of installation make it more accessible for many homeowners, though it still benefits from professional setup due to its advanced features. Compared with the RX199iN, it offers a more modest flow rate and BTU, but at a potentially lower cost, making it a good choice for those needing a reliable, space-saving solution without maximum capacity.
Pros:- Flexible indoor or outdoor installation
- High energy efficiency with UEF .97
- Smart WiFi control compatibility
Cons:- Lower flow rate than the RX199iN
- Higher cost than basic models without smart features
Best for: Medium-sized households requiring flexible indoor/outdoor installation with smart controls
Not ideal for: Very large households or users who need maximum hot water flow
- Flow Rate:9 GPM
- BTU:160,000
- Efficiency:UEF .97
- Installation:Indoor or outdoor
- Max Temperature:140°F
- Power Source:Natural Gas or Propane
Bottom line: Great for medium households wanting a reliable, flexible, and efficient water heater with smart home features.
FOGATTI Natural Gas Tankless Water Heater Indoor – Max 7.5 GPM 170,000 BTU, CSA Certified Compact Design On Demand Instant Hot Water Heater – Instagas Comfort 170S Series
The FOGATTI 170S Series offers a high flow capacity of 7.5 GPM and a robust 170,000 BTU output, making it ideal for large families or households with multiple fixtures running simultaneously. Its compact size (25 x 16.3 x 7.3 inches) allows for easy installation in tight spaces, and its advanced water servo technology maintains temperature within ±1°F, ensuring consistent comfort. Compared to the ThermoMate CZ422NG, it provides a higher flow rate but at a slightly higher energy consumption. Its CSA certification and multiple safety features emphasize durability and safe operation, although the complex setup might require professional assistance. The unit’s compatibility with low water pressure (15-150 PSI) makes it versatile. For big households needing high volume and precise temperature control, this model is a powerful option.
Pros:- High flow rate of 7.5 GPM for multiple outlets
- Precision temperature control within ±1°F
- CSA certified with multiple safety features
Cons:- Higher energy consumption compared to smaller models
- Complex installation requiring professional help
Best for: Large households or homes with high simultaneous hot water demand
Not ideal for: Small households or budget shoppers seeking basic models
- Flow Rate:7.5 GPM
- BTU:170,000
- Efficiency:CSA certified
- Installation:Indoor
- Max Temperature:140°F
- Water Pressure:15-150 PSI
Bottom line: Best for large families that need high flow capacity with reliable temperature stability and safety.
MIZUDO 180,000 BTU Natural Gas Tankless Water Heater Indoor Installation, Max 7.9 GPM, WiFi&APP Control CSA Certified Non Condensing High Efficiency for Large Families Residential Whole House
This model stands out for its impressive 7.9 GPM flow rate, making it well-suited for larger households with multiple simultaneous outlets. Compared to smaller units like the Westinghouse 120,000 BTU model, the Mizudo handles higher demand more effectively, reducing the risk of cold water during peak usage. Its advanced sealed combustion system improves indoor air quality, a key advantage over open-flame models. However, being a non-condensing heater, it sacrifices some efficiency—typically around 80-85%—which means higher operational costs over time. The Wi-Fi control feature adds convenience, but it requires a stable internet connection and compatible smartphone app. Its durable copper heat exchanger ensures longevity, but the unit’s size and installation complexity could be a hurdle for some homeowners.
Pros:- High flow rate supports multiple outlets simultaneously
- Advanced safety features like freeze protection and dry-fire safeguard
- Smart Wi-Fi control for remote operation
Cons:- Lower efficiency compared to condensing models, leading to higher energy costs
- Larger size may complicate installation in tight spaces
- Non-condensing design means more heat loss and reduced efficiency
Best for: Large families or households with high hot water demand seeking reliable, whole-house performance.
Not ideal for: Small households or apartments where space and efficiency are more critical, as this model is relatively bulky and less efficient than condensing counterparts.
- BTU Rating:180,000
- Flow Rate:7.9 GPM
- Efficiency:Approx. 85%
- Dimensions:25″ x 16.3″ x 7.3″
- Power Supply:120V
- Connections:¾” NPT
- Certifications:CSA
- Minimum Flow:0.53 GPM
Bottom line: This heater is ideal for large households needing high-volume hot water and smart control, accepting higher operational costs for capacity and reliability.
How We Picked
I evaluated these products based on several key criteria: performance capacity (GPM and BTU ratings), energy efficiency (UEF and AFUE ratings), build quality, ease of installation, and available features such as WiFi control. I prioritized models that balance high efficiency with reliable operation, especially in condensing technology. Cost and value were also significant factors, with a focus on offerings that deliver long-term savings alongside user-friendly features. The ranking reflects a blend of these factors, emphasizing models that serve different household sizes, budgets, and installation scenarios while maintaining durability and efficiency.Factors to Consider When Choosing Best Tankless Gas Water Heater Condensing
Choosing the best tankless gas water heater condensing system involves more than just comparing flow rates and prices. It’s essential to consider how the unit fits your household’s hot water demand, installation constraints, and long-term energy savings. Making a misstep here can lead to insufficient hot water, higher energy bills, or costly upgrades down the line. The following factors will help you navigate these choices and select a model that aligns with your needs.Capacity and Flow Rate
Understanding your household’s hot water demand is crucial. Measure the simultaneous flow requirements of your fixtures—showers, sinks, appliances—and select a unit with a GPM rating that comfortably exceeds this total. Oversizing can lead to unnecessary costs, while undersizing results in inadequate hot water supply. For large families or homes with multiple bathrooms, a higher flow rate, such as 9-11 GPM, is usually preferable.
Efficiency and Operating Costs
Condensing models are designed to maximize energy efficiency, often achieving AFUE ratings over 95%. This translates into lower utility bills over time, but they tend to have higher upfront costs. It’s wise to evaluate the long-term savings potential versus initial investment. Also, consider the climate—some models perform better in colder environments, which can impact efficiency and reliability.
Installation and Space Requirements
Indoor units may require venting and sufficient clearance, making installation more complex and costly. Outdoor units offer easier setup and are less prone to indoor space constraints, but they need to withstand weather conditions. Ensure your home’s infrastructure can support the chosen model’s installation needs, including venting, gas supply, and electrical connections.
Additional Features
Modern condensing units often include WiFi connectivity, remote control, and diagnostic alerts. These features add convenience and can simplify maintenance, but they usually come at a higher price. Decide if these extras align with your comfort level and budget, or if they are non-essential for your household.
Brand Reputation and Support
Research manufacturer reputation, warranty coverage, and customer support quality. Reliable brands like Rinnai and Rheem tend to offer better long-term service and parts availability. A well-supported product can prevent headaches and costly repairs, especially for high-capacity units that see frequent use.
Frequently Asked Questions
How do I determine the right flow rate for my household?
To find the appropriate flow rate, add up the GPM requirements of all fixtures that may run simultaneously. For example, a shower typically uses around 2-2.5 GPM, while a dishwasher might use 1.5 GPM. If multiple fixtures are used at once, choose a unit with a GPM rating that exceeds this total to ensure consistent hot water supply without pressure drops.
Are condensing tankless water heaters worth the extra cost?
Condensing models generally have higher upfront costs but deliver superior energy efficiency, which can lead to significant savings over their lifespan. If your household uses hot water frequently or lives in a colder climate, investing in a condensing unit makes sense. For occasional use or smaller households, a non-condensing model might be more budget-friendly with acceptable performance.
Can I install a condensing water heater outdoors?
Yes, many condensing models are designed for outdoor installation, offering the advantage of easier setup and no indoor space constraints. However, outdoor units must be rated for weather resistance and proper venting to prevent damage. Confirm the specific model’s outdoor suitability and ensure your home’s setup can support outdoor installation.
How often do I need to perform maintenance on these units?
Routine maintenance for condensing tankless water heaters includes flushing to remove mineral buildup, inspecting venting, and checking for leaks. Typically, annual maintenance helps ensure efficiency and longevity. Some models include diagnostic features that can alert you to issues early, reducing the risk of costly repairs or downtime.
Is it better to get a unit with WiFi features?
WiFi-enabled models provide remote control, monitoring, and diagnostic alerts, which can enhance convenience and simplify maintenance. However, these features often come at a higher initial cost. If you prefer tech-savvy solutions and want to optimize performance remotely, opting for a WiFi model makes sense; otherwise, a simpler unit may suffice.
Conclusion
For households seeking the best overall performance, the Rinnai RX199iN offers exceptional capacity and advanced features, making it ideal for large families. Budget-conscious buyers will find the Westinghouse provides reliable condensing technology at a lower cost. Those prioritizing long-term savings should consider models like the Rheem RTG-70DVLN-3 or Rinnai RX130iN, which combine efficiency with solid performance. For beginners or smaller homes, a compact and simpler unit might be the best choice, while large families or high-demand households benefit from larger capacity models like the Rinnai RX199iN. Ultimately, your selection depends on your household size, budget, and specific installation needs.
