When searching for a tankless water heater, the goal is to find a reliable, efficient, and appropriately sized unit that fits your household needs. The best overall pick is the Rinnai RX199iN, known for its impressive flow rate and smart features. For those on a budget, the EcoSmart ECO 11 offers solid performance at a lower price, while the Novieex model is ideal for indoor use and straightforward installation. The main tradeoffs involve balancing flow capacity, energy source compatibility, upfront cost, and long-term efficiency. Continue reading for a full breakdown of these options and how to choose the right unit for your home.
Key Takeaways
- Flow rate capacity varies significantly, influencing suitability for different household sizes.
- Gas models generally offer higher flow rates but can be more complex and costly to install than electric options.
- Electric units are often more compact and easier to install but may struggle with higher demand or larger households.
- Smart features like Wi-Fi control enhance usability but typically come with higher price tags.
- Durability and brand reputation are key factors in long-term satisfaction and maintenance costs.
More Details on Our Top Picks
Natural Gas Tankless Water Heater, Indoor, 3.6 GPM, 85,000 BTU, CSA Certified
This model stands out for its compact size and energy-efficient operation, making it ideal for small households or apartments. Compared with larger units like the Rinnai RX199iN, it offers a lower flow rate, which limits simultaneous usage but keeps installation straightforward and costs lower. Its 85,000 BTU ensures reliable hot water for basic household needs, though it struggles in high-demand situations or high-altitude areas. The unit’s safety features and CSA certification add peace of mind, but professional installation is a must since venting and water connections aren’t included. It’s a smart choice for those who prioritize space-saving design and moderate hot water needs at a lower price point.
Pros:- Compact design fits small spaces and apartments
- Energy-efficient on-demand heating reduces utility bills
- Advanced safety features ensure reliable operation
Cons:- Requires professional installation due to venting and water connections
- Not suitable for high-altitude locations above 2000 feet
Best for: Small households or apartments needing reliable hot water without space for larger units
Not ideal for: Large families or homes with multiple high-demand fixtures, due to its limited flow rate
- Flow Rate:3.6 GPM
- BTU:85,000
- Connector Size:1/2″ NPT
- Voltage:120V
- Certification:CSA Certified
- Installation Notes:Must be installed by a licensed plumber; not for areas above 2000 feet elevation
Bottom line: This heater is best for small-space dwellers seeking reliable, efficient hot water without the need for high flow rates.
Natural Gas Tankless Water Heater, 4.21 GPM, Indoor, Instant Hot Gas Water Heater with Multi-Protection
This unit offers a higher flow rate of 4.21 GPM, making it more suitable for small to medium households compared to the 3.6 GPM model. Its multi-protection features and durable stainless steel body enhance safety and longevity, outperforming basic models like the first in safety features while providing more consistent hot water. However, it still requires proper ventilation and professional installation, similar to other gas units, and isn’t compatible with propane or outdoor setups. Its maximum temperature of 149°F and high efficiency make it a strong choice for households that need reliable hot water without the bulk of larger units like the Rinnai RX199iN. It strikes a good balance between capacity and safety, ideal for those prioritizing reliability and safety features.
Pros:- Higher flow rate supports multiple fixtures simultaneously
- Includes multiple safety protections for peace of mind
- Durable stainless steel and copper construction
Cons:- Requires proper ventilation and professional installation
- Limited to natural gas only, no propane option
Best for: Moderate-sized households seeking a safe, reliable natural gas heater with better flow capacity
Not ideal for: Homes in high-altitude areas or those not equipped with proper ventilation, due to safety and performance considerations
- Flow Rate:4.21 GPM
- Maximum Temperature:149°F
- Power:68,000 BTU/hr
- Material:Copper, Stainless Steel
- Water Pressure:3.6 PSI
- Temperature Range:95°F to 149°F
Bottom line: This heater is well-suited for households needing more hot water with added safety features in a compact form.
Rheem 18kW 240V Tankless Electric Water Heater, Gray
The Rheem RTEX-18 makes a compelling case for small-scale applications with its compact design and digital controls. Its maximum flow rate of 4.4 GPM rivals some gas models, but it’s best suited for single fixtures or small households, unlike larger units like the Rheem RTEX-24 that can handle whole-home needs. The self-modulating technology helps cut energy costs by adjusting power based on demand, which is a plus for energy-conscious buyers. However, its electrical requirements—240V and significant amperage—can complicate installation, making it less ideal for those without proper electrical wiring. This pick excels for point-of-use or small household setups where space is limited and energy savings are prioritized.
Pros:- Space-saving, compact design
- Energy-efficient self-modulating technology
- Digital LED display for precise temperature control
Cons:- Limited flow rate of 4.4 GPM may not meet high-demand needs
- Installation may require professional electrical work
Best for: Apartment dwellers or small households needing point-of-use hot water without space for larger units
Not ideal for: Large families or homes needing high flow rates for multiple fixtures simultaneously
- Brand:Rheem
- Model:Professional Classic RTEX-18
- Wattage:18,000 watts
- Voltage:240V
- Maximum Flow Rate:4.4 GPM
- Efficiency:99.8%
Bottom line: Ideal for small spaces where point-of-use hot water is needed, with energy savings a bonus.
Rheem Performance RTEX-11 11kW 240V Tankless Electric Water Heater
The Rheem RTEX-11 offers a compact, affordable solution for specific hot water needs, such as under-sink or small point-of-use applications. Its modest flow rate of 2.68 GPM limits its use for whole-house heating, unlike the higher-capacity RTEX-18 or RTEX-24. The digital temperature control and self-modulating technology make it easy to operate and energy-efficient for low-demand scenarios. Its 11 kW power draw requires a dedicated electrical circuit, which could be a concern for some installations. This model is best for those who need a reliable, space-saving heater for limited tasks rather than whole-home hot water supply.
Pros:- Compact, space-efficient design
- Provides continuous hot water for small applications
- Digital temperature control for precision
Cons:- Flow rate limited to 2.68 GPM, not suitable for large households
- Requires specific electrical setup with dedicated circuit
Best for: Homeowners needing a small, reliable heater for under-sink or localized hot water tasks
Not ideal for: Large households or those seeking whole-house hot water solutions
- Power Source:AC
- Wattage:11 KW
- Voltage:240 V
- Flow Rate:2.68 GPM
- Efficiency:99.8%
- Maximum Pressure:150 PSI
Bottom line: Perfect for small-scale applications where space and energy efficiency matter most.
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
The Rheem RTEX-24 stands out by delivering enough capacity to serve an entire household, making it a top choice for electric-powered homes aiming for whole-house hot water. Its 24 kW power and 2 GPM flow rate at peak make it suitable for medium to larger homes, especially when paired with appropriate electrical service—specifically, a 100A circuit. Compared to smaller electric models, it offers greater capacity but demands complex electrical work, which can increase installation costs. Its adjustable temperature control from 80°F to 140°F and space-efficient design make it a versatile option, though its performance can fluctuate based on groundwater temperature, much like other electric units. It excels where electrical infrastructure supports high wattage units and space is limited.
Pros:- Provides continuous hot water for entire home
- Adjustable temperature control in fine increments
- Space-efficient and energy-conscious design
Cons:- Requires specific electrical setup with 3 x 40A breakers
- Performance varies with groundwater temperature
Best for: Homes with adequate electrical capacity needing reliable whole-house hot water
Not ideal for: Properties with limited electrical capacity or where electrical upgrades are not feasible
- Model:RTEX-24
- Power:24 kW
- Voltage:240 V
- Ampere:100 A
Bottom line: This heater is a strong choice for electric homes with sufficient electrical capacity for whole-house hot water needs.
Novieex Tankless Water Heater, Natural Gas, 4.3 GPM, 100,000 BTU, Indoor Wall-Mount, LED Display
This model from Novieex stands out for its balance of high flow rate and safety features, making it ideal for families needing reliable indoor hot water. Compared with the Rinnai RX199iN, it offers a slightly lower maximum flow rate but excels in safety protections like anti-freezing and flame failure, which are crucial for indoor settings. The digital LED display and precise temperature control enhance user comfort, while its 100,000 BTU output ensures quick hot water delivery. The main tradeoffs are its dependence on natural gas—unlike electric options—and the requirement for professional installation due to venting and gas connections. This makes it perfect for those prioritizing high capacity and safety but with the space and gas supply to support it.
Pros:- Provides instant hot water with a high flow rate suitable for multiple fixtures
- Precise temperature control with digital thermostat for comfort and safety
- Space-saving wall-mounted design ideal for indoor use
- Built-in safety protections ensure reliable operation
Cons:- Requires professional installation due to gas and venting needs
- Limited to indoor use only
Best for: Homeowners with natural gas lines seeking a high-capacity, reliable indoor heater for multiple fixtures
Not ideal for: Renters or small households without natural gas supply, as installation and gas connection are mandatory
- Power Source:Natural Gas
- Flow Rate:4.3 GPM
- Maximum Temperature:149°F
- Heat Output:100,000 BTU
- Efficiency:High Efficiency
- Mount Type:Wall
Bottom line: This heater suits households that need consistent high-volume hot water and have gas access, despite installation complexity.
18kW Tankless Electric Water Heater 240V WINTEMP, On Demand Instant Hot Water, WiFi Control, 4.3 GPM, ETL Certified
The WINTEMP 18kW electric heater excels in providing instant hot water without preheating delays, making it ideal for smaller households or secondary applications. Compared to the EcoSmart ECO 11, it offers a similar flow rate but with a higher wattage for greater capacity, though it demands a dedicated 240V circuit and significant electrical capacity—limiting its installation options. Its WiFi control adds convenience for remote adjustments, and safety features like leakage and dry-fire protections enhance reliability. The tradeoff is its limited support for multiple simultaneous outlets, which makes it less suited for larger homes. This pick makes the most sense for users who value smart features and energy savings in a compact, electric package.
Pros:- Instant hot water with no preheating required
- Energy-efficient with up to 99% savings
- Space-saving wall-mounted design
- WiFi control for remote temperature management
Cons:- Requires specific electrical wiring and breakers
- Limited to 2-3 outlets at a time
Best for: Small households or point-of-use settings with existing 240V wiring seeking energy-efficient hot water
Not ideal for: Large families or homes with multiple simultaneous hot water demands, due to flow rate limits
- Power:18KW
- Voltage:240V
- Flow Rate:Up to 4.3 GPM
- Water Connection:3/4″ NPT
- Dimensions:11.1″ W x 19.1″ L x 4″ H
- Safety Certifications:ETL
Bottom line: This electric heater is best for energy-conscious small households or point-of-use applications with smart control needs.
Rinnai RX199iN Condensing Smart Sense Tankless Water Heater, Indoor/Outdoor, Up to 11.1 GPM, 199,000 BTU
The Rinnai RX199iN offers impressive capacity and flexibility, supporting up to 11.1 GPM, making it ideal for larger households or outdoor installations. Its compact design saves space, and high efficiency with a UEF of .98 helps reduce operating costs compared to less efficient models like the electric WINTEMP. The ability to install it indoors or outdoors broadens its application, though outdoor setups require venting and a vent cap. Wi-Fi compatibility is available but requires a separate module, which adds cost. Compared to the Novieex gas heater, it offers higher flow capacity and outdoor versatility, but at a higher initial price and with more complex installation. This model makes sense for those wanting maximum hot water with flexible placement options.
Pros:- High flow rate supports multiple fixtures simultaneously
- Supports both natural gas and propane for versatility
- Indoor/outdoor installation flexibility
- High energy efficiency with UEF .98
Cons:- Wi-Fi control requires purchase of separate control module
- Professional installation recommended due to venting and setup
Best for: Large households needing high hot water flow and outdoor or indoor installation flexibility
Not ideal for: Consumers seeking a simple, plug-and-play solution or with strict budget constraints
- Flow Rate:Up to 11.1 GPM
- BTU:199,000
- Gas Type:Natural Gas or Propane
- Efficiency:UEF .98
- Installation:Indoor or Outdoor
Bottom line: Ideal for large homes requiring high-capacity, flexible installation, though with a higher upfront cost and complex setup.
Natural Gas Tankless Water Heater, 5.26 GPM, Outdoor, Digital Display, Multi-Protection
This outdoor natural gas heater offers a reliable flow rate of 5.26 GPM, balancing capacity with durability through stainless steel construction. It provides precise temperature control via a digital display, similar to the Novieex indoor model but optimized for outdoor use. Its active heating and anti-freeze features make it suitable for outdoor environments, though its review ratings are mixed, suggesting some users encounter reliability or installation issues. Compared to the smaller capacity EcoSmart ECO 11, it supports higher flow but at a higher cost, and its outdoor-only design limits use indoors. It’s best for homeowners who need tough, outdoor-ready equipment capable of supporting whole-house demand, provided they are comfortable with the higher price and mixed user feedback.
Pros:- Provides instant hot water with a decent flow rate
- Durable stainless steel and corrosion-resistant construction
- Digital display for precise temperature control
- Active heating and anti-freeze protections
Cons:- Mixed user reviews indicating some reliability concerns
- Higher price point compared to smaller electric models
Best for: Homeowners needing durable, outdoor-supported gas hot water for whole-house use
Not ideal for: Urban dwellers or renters with limited outdoor space or requiring indoor installation
- Flow Rate:5.26 GPM
- Maximum Temperature:149°F
- BTU:120,000 BTU
- Material:Stainless Steel
- Mounting Type:Wall
Bottom line: Suitable for outdoor whole-house hot water needs with durable build, despite some mixed feedback on reliability.
Natural Gas Tankless Water Heater, 5.26 GPM, Outdoor, Digital Display, Multi-Protection
This outdoor natural gas heater offers a reliable flow rate of 5.26 GPM, balancing capacity with durability through stainless steel construction. It provides precise temperature control via a digital display, similar to the Novieex indoor model but optimized for outdoor use. Its active heating and anti-freeze features make it suitable for outdoor environments, though its review ratings are mixed, suggesting some users encounter reliability or installation issues. Compared to the smaller capacity EcoSmart ECO 11, it supports higher flow but at a higher cost, and its outdoor-only design limits use indoors. It’s best for homeowners who need tough, outdoor-ready equipment capable of supporting whole-house demand, provided they are comfortable with the higher price and mixed user feedback.
Pros:- Provides instant hot water with a decent flow rate
- Durable stainless steel and corrosion-resistant construction
- Digital display for precise temperature control
- Active heating and anti-freeze protections
Cons:- Mixed user reviews indicating some reliability concerns
- Higher price point compared to smaller electric models
Best for: Homeowners needing durable, outdoor-supported gas hot water for whole-house use
Not ideal for: Urban dwellers or renters with limited outdoor space or requiring indoor installation
- Flow Rate:5.26 GPM
- Maximum Temperature:149°F
- BTU:120,000 BTU
- Material:Stainless Steel
- Mounting Type:Wall
Bottom line: Suitable for outdoor whole-house hot water needs with durable build, despite some mixed feedback on reliability.
How We Picked
The products in this roundup were selected based on a combination of performance, build quality, ease of installation, energy source compatibility, and overall value. We prioritized units with verified safety certifications, reliable customer feedback, and features that cater to different household sizes and budgets. The ranking reflects how well each model balances flow capacity, energy efficiency, and upfront costs, helping buyers find the best fit for their specific needs. We aimed to include a range of electric and gas options, from budget-friendly to premium models, ensuring broad relevance for various buyers.Factors to Consider When Choosing Tankless Water Heater
Choosing the right tankless water heater requires considering multiple factors beyond just capacity and price. Size and flow rate are critical to meet household hot water demands without overspending. Energy source compatibility—gas versus electric—affects installation complexity and ongoing costs. Efficiency ratings influence long-term savings, while features like Wi-Fi control or multi-protection systems can add convenience and safety. Understanding these considerations helps prevent common mistakes, such as underestimating capacity or choosing incompatible fuel types.Flow Rate and Household Size
Matching the heater’s flow rate to your household’s hot water needs is essential. Larger families or homes with multiple bathrooms typically require units with higher GPM ratings, like the Rinnai RX199iN, to prevent cold showers. Smaller households may get by with lower-capacity models, which are usually more affordable and easier to install. Overestimating capacity can lead to unnecessary costs, while underestimating can cause inadequate hot water supply during peak usage times.
Fuel Type: Gas vs. Electric
Gas-powered units generally provide higher flow rates and are better suited for larger households or heavy usage. However, they require proper ventilation and tend to be more complex to install. Electric models are simpler, often more compact, and easier to retrofit into existing homes, but they may struggle with higher demands, especially in colder climates where incoming water is colder. Your choice depends on existing infrastructure, local fuel costs, and long-term energy expenses.
Size and Installation Space
Consider the physical dimensions of the unit relative to your available space. Electric models like the EcoSmart ECO 11 are compact enough for tight spaces, making them ideal for apartments or small homes. Gas units, especially high-capacity models, require more space and proper venting. Installing a larger unit in a cramped area can lead to additional costs or safety concerns, so measure carefully and plan for proper ventilation if needed.
Efficiency and Operating Costs
Energy efficiency ratings, such as UEF (Uniform Energy Factor), influence monthly bills and environmental impact. Condensing gas models like the Rinnai RX199iN tend to be more efficient, reducing operating costs over time. Electric units are often rated for high efficiency but may have higher electricity usage depending on your local rates. Investing in a more efficient unit can pay off in savings, but consider initial costs versus long-term benefits.
Smart Features and Safety
Features like Wi-Fi control, multi-protection systems, and digital displays add convenience and safety. Units like the WINTEMP model with Wi-Fi allow remote monitoring and settings adjustments, which can be helpful for maintenance and troubleshooting. Safety features such as overload protection and leak detection are important for peace of mind, especially in homes with young children or older occupants. Weigh these extras against budget constraints and personal preferences for tech integration.
Frequently Asked Questions
Can a tankless water heater supply hot water to multiple fixtures at once?
Yes, but the capacity depends on the unit’s flow rate. A high-GPM model like the Rinnai RX199iN can handle simultaneous showers, faucets, and appliances, making it suitable for larger households. Lower-capacity models may struggle under heavy demand, leading to cold water during peak usage. Always match the unit’s flow rate to your household’s maximum hot water needs to prevent frustration and ensure consistent comfort.
Is it better to choose a gas or electric tankless water heater for my home?
The decision depends on your home’s existing infrastructure, climate, and energy costs. Gas units typically offer higher flow rates and are better for large households, but they require proper venting and more complex installation. Electric models are simpler, smaller, and may be more cost-effective for small homes or apartments, but they can be limited in capacity. Consider your household’s water demand and local utility rates when making this choice.
How do I know what size tankless water heater I need?
The size depends on your household’s peak hot water demand. Calculate the GPM needed for all fixtures used simultaneously, then select a unit with a matching or higher flow rate. For example, a standard shower requires about 2-2.5 GPM, while multiple fixtures or appliances increase demand. It’s better to slightly oversize than undersize to ensure consistent hot water supply during busy periods.
Are electric tankless water heaters suitable for large households?
Electric units generally have lower flow capacities, making them less ideal for large households with multiple simultaneous hot water demands. However, models like the Rheem RTEX-24 or WINTEMP offer higher GPM ratings suitable for moderate use. For very large households, gas models are typically more reliable due to their higher capacity and flow rates. Always match the unit’s specifications to your household’s specific needs.
What maintenance do tankless water heaters require?
Tankless water heaters require periodic flushing to remove mineral buildup, especially in areas with hard water. Checking and replacing filters, inspecting vents, and ensuring proper venting are also part of routine maintenance. Most modern units include diagnostic displays to alert you to potential issues, which can help prevent costly repairs. Regular maintenance extends the lifespan of the unit and maintains efficiency over time.
Conclusion
For most households, the Rinnai RX199iN offers the best overall performance with high flow capacity and smart features, making it ideal for larger families or demanding usage. Budget-conscious buyers might prefer the EcoSmart ECO 11 for its affordability and compact size, while those seeking ease of installation and straightforward operation will find the Novieex model a strong fit. If you prioritize premium features and maximum efficiency, a gas condensing unit like the Rinnai or Novieex may justify the higher investment. New homeowners or renters should consider electric options for simplicity, while large households should prioritize higher GPM gas models. Each choice hinges on your specific hot water needs, space, and budget constraints.
