For those searching for the best tankless water heaters, the key factors often boil down to capacity, energy efficiency, and ease of installation. The Rinnai RX199iN stands out as the best overall pick for its high GPM and smart features, ideal for larger households. The Stiebel Eltron Tempra 29 Plus is a top electric choice, known for its reliability and advanced technology. However, these units come with tradeoffs: higher capacity models tend to be more expensive and require professional installation, while smaller units may struggle to supply multiple fixtures simultaneously. Continue reading for a detailed breakdown of each option and what makes it suitable for different needs.
Key Takeaways
- High-GPM models like the Rinnai RX199iN excel for large households needing simultaneous hot water supply.
- Electric models generally cost less upfront but may have limited capacity, making them better for small homes or point-of-use scenarios.
- Condensing gas units offer superior efficiency but come with higher installation complexity and cost.
- Features like LED displays and smart controls add convenience but often increase price.
- Installation requirements and fuel type are critical considerations that impact long-term performance and costs.
More Details on Our Top Picks
Tankless Water Heater, Novieex On Demand Water Heater Natural Gas, Up to 4.3 GPM, 100,000 BTU Instant Hot Water Heater with LED Display, Indoor Installation, 2-4 Point Use for Family Bathroom Kitchen
This natural gas-powered model stands out for its balance of power, reliability, and space efficiency. Compared to the Rheem 18kW electric option, it delivers higher flow rates and is better suited for households that need multiple fixtures simultaneously, especially in colder climates where gas heating performs more consistently. Its precise temperature control and multi-protection system add safety and comfort, but professional installation is a must due to gas hookup requirements. The unit’s compact wall-mounted design makes it ideal for utility spaces without sacrificing performance. While it’s not suitable for very small homes or those with only one bathroom, its capacity and safety features make it a practical choice for families needing reliable hot water without the bulk of traditional tanks.
Pros:- Powerful 100,000 BTU gas burner provides ample hot water for multiple fixtures
- Space-saving wall-mounted design ideal for limited areas
- Precise digital thermostat ensures consistent water temperature
- All-round safety protections including gas leak and freeze safeguards
Cons:- Requires professional installation and gas connection, increasing upfront cost
- Bulky setup compared to smaller electric models
Best for: Families in need of reliable hot water for multiple fixtures in medium-sized homes, especially where space and safety matter.
Not ideal for: Small apartments or single-bathroom setups where lower capacity or electric options might be more cost-effective.
- Flow Rate:4.3 GPM
- BTU:100,000
- Power Source:Natural Gas
- Maximum Temperature:149°F
- Efficiency:High Efficiency
- Mount Type:Wall
Bottom line: This model suits households that need robust, on-demand gas hot water and have space for professional setup.
14kW Tankless Water Heater Electric, ORBEK On Demand Instant Hot Water Heater 240V, Max 3.38 GPM, Supply for 1-2 Fixtures, ETL Certified, Indoor Installation, New Upgraded 2.0
This electric model is designed for compact spaces and light usage, making it a good fit for apartments or small cottages where only 1-2 fixtures need hot water at a time. Unlike the Stiebel Eltron Tempra 29 Plus, which offers higher flow rates, the ORBEK is limited to around 3.38 GPM, so it’s not suitable for larger households. Its advanced safety features and ETL certification provide peace of mind, but it demands a dedicated 240V/60A circuit with proper wiring, which can complicate installation. The intuitive LED display and stable temperature control mean users can easily set and monitor hot water, but power requirements mean this isn’t ideal for homes with outdated electrical panels.
Pros:- Compact, space-efficient design
- LED display allows easy temperature adjustment
- Uses up to 60% less electricity than traditional tanks
- ETL certified with multiple safety protections
Cons:- Limited flow rate makes it unsuitable for multiple fixtures
- Requires a significant electrical capacity (60A breaker) which may need upgrade
- Not ideal for larger households or high-demand scenarios
Best for: Single or couple households, small apartments, or guest houses with minimal fixture demand.
Not ideal for: Large families or homes with multiple bathrooms needing high flow rates or simultaneous use.
- Flow Rate:3.38 GPM
- Power:14kW
- Voltage:240V
- Max Temperature:140°F
- Efficiency:Up to 60% savings
- Installation:Indoor
Bottom line: This electric heater is perfect for small spaces with low hot water demand and a modern electrical setup.
Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater
This German-engineered unit excels in delivering consistent, on-demand hot water with impressive energy savings—up to 34% compared to traditional electric heaters. Its high efficiency and no-venting design make it a straightforward choice for homes with 2-3 bathrooms in warmer climates. Compared to the Rheem 18kW, the Tempra 29 Plus offers slightly lower flow rate at 3 GPM but makes up for it with superior temperature stability and less wattage. Installation requires dedicated electrical service, making it less suitable for older homes, but its space-saving design and reliable performance make it ideal for eco-conscious households seeking efficiency without sacrificing capacity.
Pros:- Energy savings of up to 34%
- No venting needed, simplifying installation
- Compact and space-efficient design
- German engineering ensures consistent temperature control
Cons:- Requires high-capacity electrical service (3x40A breakers)
- Complex installation due to high wattage requirements
- Limited flow rate for larger households
Best for: Homes with 2-3 bathrooms in warm climates where energy savings and reliable performance are priorities.
Not ideal for: Large households in cold climates or homes with limited electrical capacity due to high power demands.
- Power Source:Electric
- Wattage:28.8 kW
- Voltage:240V
- Flow Rate:3 GPM
- Efficiency:99%
- Mount Type:Wall
Bottom line: This model suits eco-conscious homeowners seeking reliable, efficient hot water for moderate household needs.
Rheem 18kW 240V Tankless Electric Water Heater, Gray
The Rheem 18kW electric tankless heater offers a straightforward, reliable solution for small to medium households. Its digital thermostatic control with a precise ±1°F accuracy allows for easy temperature management, similar to the EcoSmart ECO 11, but with slightly higher wattage capacity. The self-modulating feature adjusts power to meet demand, conserving energy, but the high wattage and need for dedicated circuit breakers mean installation can be challenging in older homes. Its durable copper heating elements ensure longevity, and the simple bottom-threaded connections make setup easier for DIYers with electrical experience. While it doesn’t match the flow rate of gas models, it provides a practical electric solution for homes with limited space and electrical capacity.
Pros:- Reliable digital temperature control
- Self-modulating for energy efficiency
- Durable copper heating elements
- Simple bottom connection for easy installation
Cons:- High electrical demand requiring dedicated breaker
- Limited flow rate at 3 GPM
- Less suitable for large households with multiple fixtures
Best for: Small to medium-sized households seeking dependable electric hot water with easy digital control.
Not ideal for: Homes requiring high flow rates or multiple simultaneous fixtures, where gas or higher-capacity units are necessary.
- Power:18kW
- Voltage:240V
- Flow Rate:Up to 4.4 GPM
- Efficiency:High
- Mount Type:Wall
- Color:Gray
Bottom line: This electric heater offers dependable, precise hot water for smaller homes with adequate electrical infrastructure.
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
The Rinnai RX199iN is a versatile, high-capacity gas tankless water heater that handles large households effortlessly, with a maximum flow of 11.1 GPM—making it ideal for homes with multiple bathrooms or heavy water demand. Its Smart Sense gas control and condensing technology offer high efficiency and adaptability for indoor or outdoor installation, surpassing smaller electric units such as the Stiebel Eltron Tempra 29 Plus in capacity. The sleek design includes WiFi control, and its durable construction supports long-term, heavy-duty use. The requirement for professional installation and venting makes it less suitable for DIY projects, but for large homes, this heater provides consistent, endless hot water with excellent energy efficiency and flexibility.
Pros:- High flow rate of 11.1 GPM for large households
- Indoor or outdoor installation flexibility
- High energy efficiency with condensing technology
- WiFi control and modern interface
Cons:- Requires professional installation and venting
- Higher upfront cost and complexity
- Size may be overkill for small homes
Best for: Large households or homes with high simultaneous fixture use, especially where indoor/outdoor installation flexibility is needed.
Not ideal for: Small apartments or homes with limited space and low hot water demand, where a smaller electric unit would suffice.
- Flow Rate:11.1 GPM
- BTU:199,000
- Fuel Type:Natural Gas or Propane
- Maximum Pressure:150 PSI
- Efficiency:UEF .98
- Installation Options:Indoor/Outdoor
Bottom line: This model is a top choice for large families needing reliable, high-capacity hot water with flexible installation options.
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
This Rheem model stands out for delivering continuous hot water across a whole home, outperforming smaller units like the Rheem RTEX-11 in capacity and flow rate. Its 24kW power output ensures sufficient flow for multiple fixtures, but the high electrical demand requires a robust panel with three 40A double pole breakers—something not suitable for all homes. Compared to the EcoSmart ECO 11, this unit offers more power but involves more complex installation and higher upfront electrical costs. The space savings are significant, and the performance is reliable, yet the installation complexity and electrical requirements are tradeoffs. This pick makes the most sense for homeowners upgrading to a dedicated, high-capacity system who have space and electrical capacity.
Specs: Power Source: Corded Electric, Wattage: 24 KW, Voltage: 240V, Flow Rate: 5.9 GPM, Max Temp: 140°F, Efficiency: 99.8%- Pros: Highly reliable, capable of supporting multiple fixtures, compact design for a whole house
- Cons: Significant electrical wiring needed, high initial installation cost, requires space in the breaker panel
Verdict: Best suited for homeowners with existing electrical capacity seeking dependable whole-home hot water.
Pros:- Provides continuous hot water for the entire home
- High flow rate supports multiple fixtures simultaneously
- Compact size saves space
Cons:- Requires significant electrical panel capacity and wiring
- Higher upfront installation complexity and cost
- Needs professional installation
Best for: Homeowners upgrading to high-capacity, whole-house hot water systems with ample electrical panel space
Not ideal for: Small homes or apartments lacking sufficient electrical capacity and space for complex wiring
- Power Source:Corded Electric
- Wattage:24 KW
- Voltage:240V
- Flow Rate:5.9 GPM
- Max Temperature:140°F
- Efficiency:99.8%
Bottom line: This model is ideal for large households with existing electrical capacity needing reliable, high-flow hot water.
27kW Tankless Water Heater Electric, APUS 240V On Demand Instant Hot Water with Memory Function & LED Display
This APUS model offers a powerful 27kW output with a sleek, compact design, making it well suited for smaller spaces compared to larger, bulkier units like the Rheem RTEX-24. It supports up to 6.5 GPM, enough for multiple simultaneous uses in a typical household, but requires a dedicated 3×40A circuit, similar to the Rheem, which might be a challenge for some homes. Its self-modulating technology and memory function enhance efficiency and user convenience, and it’s designed for easy wall mounting. Unlike the EcoSmart ECO 11, which is limited to lower flow rates, this unit supports higher demand, but its electrical demands mean it’s best for homes with suitable wiring and space for the installation. This choice makes sense for households needing a compact, high-capacity solution without sacrificing space.
Specs: Power Source: 240V, Wattage: 27,000W, Flow Rate: 6.5 GPM, Max Temp: 140°F, Efficiency: 99.8%, Mount Type: Wall- Pros: High flow rate supports multiple fixtures, space-efficient design, advanced digital controls with memory function
- Cons: Demands a robust electrical setup, installation may require professional help, slightly higher cost
Verdict: Ideal for small to medium households seeking high capacity in a compact form factor.
Pros:- Supports up to 6.5 GPM for multiple outlets
- Space-saving, wall-mounted design
- Smart control with memory for user preferences
Cons:- Requires a 3×40A dedicated circuit
- Installation complexity and cost
- Higher power consumption
Best for: Families or apartments needing a high-capacity, space-efficient solution for multiple fixtures
Not ideal for: Homes without sufficient electrical wiring or space for a 27kW unit
- Power Source:240V
- Wattage:27,000W
- Flow Rate:6.5 GPM
- Max Temp:140°F
- Efficiency:99.8%
- Mount Type:Wall
Bottom line: Best for small to medium households needing reliable, high-flow hot water in limited space.
Rheem 11kW 240V Tankless Electric Water Heater
This Rheem unit offers a straightforward, space-efficient solution for single fixtures or small households, supporting up to 2.68 GPM, which is similar to the EcoSmart ECO 11 but with a lower wattage. Its compact size and simple ON/OFF control make it ideal for under-sink or small bathroom use, but it’s not suitable for whole-house applications where higher flow is needed. Its 11kW power output limits capacity compared to the larger Rheem models, but it is easier to install and consumes less electrical power—making it a good choice for small spaces or secondary points of use. The unit’s 99.8% efficiency is comparable to others, but it’s designed specifically for low-demand scenarios. This makes it well-suited for users who need dependable hot water at a single fixture without the complexity of high-capacity systems.
Specs: Power Source: 240V, Wattage: 11,000W, Flow Rate: 2.68 GPM, Max Temp: 140°F, Efficiency: 99.8%, Mount Type: Wall- Pros: Compact and easy to install, ideal for point-of-use, low electrical demand
- Cons: Limited flow rate, not suitable for whole-house needs, lower capacity
Verdict: Best for individuals or small households needing reliable point-of-use hot water without high electrical demands.
Pros:- Compact and easy to install
- Energy-efficient with high thermal performance
- Low electrical demand suitable for secondary points
Cons:- Limited flow rate for larger household needs
- Not suitable for whole-house hot water supply
- Supports only a single fixture at a time
Best for: Single fixture or small apartment applications where space and electrical load are limited
Not ideal for: Large households or homes requiring multiple simultaneous hot water outlets
- Power Source:240V
- Wattage:11,000W
- Flow Rate:2.68 GPM
- Max Temp:140°F
- Efficiency:99.8%
- Mount Type:Wall
Bottom line: Perfect for point-of-use needs in small homes or apartments with limited electrical capacity.
EcoSmart ECO 11 Electric Tankless Water Heater, 13KW at 240 Volts
The EcoSmart ECO 11 provides reliable on-demand hot water for small applications, supporting up to 1.3 GPM in colder climates, which is less than the Rheem RTEX-11 but at a more affordable price point. Its self-modulating technology offers improved efficiency, and its 90% smaller size makes it ideal for tight spaces or point-of-use installation. While it’s perfect for a single bathroom sink or small laundry, its flow rate drops significantly in colder water, limiting its use in larger households. The unit’s 99% efficiency and simple wall-mount design make it an excellent entry-level choice, but it’s not suitable for whole-house use or multiple fixtures at once. For users prioritizing cost and space over capacity, this model is a practical option that balances performance with affordability.
Specs: Power Source: 240V, Wattage: 13KW, Flow Rate: 1.3 GPM, Max Temp: 140°F, Efficiency: 99%, Mount Type: Wall- Pros: Very affordable, compact and space-saving, energy-efficient
- Cons: Low flow rate in cold water, only suitable for small applications, limited to one fixture
Verdict: Best for budget-conscious users needing a reliable point-of-use water heater with minimal space requirements.
Pros:- Very budget-friendly price
- Compact size fits tight spaces
- High efficiency reduces energy costs
Cons:- Limited flow rate, especially in cold water
- Not designed for whole-house or multi-fixture use
- Flow drops with colder inlet water
Best for: Individuals or small spaces needing a low-cost, point-of-use hot water solution
Not ideal for: Large households or multiple fixtures simultaneously
- Power Source:240V
- Wattage:13KW
- Flow Rate:1.3 GPM
- Max Temp:140°F
- Efficiency:99%
- Mount Type:Wall
Bottom line: A solid, affordable choice for small-scale point-of-use hot water needs in tight spaces.
How We Picked
The products in this roundup were evaluated based on performance, capacity, energy efficiency, build quality, ease of installation, and value for money. Priority was given to models that reliably supply hot water for typical household needs, with a focus on balancing capacity and energy consumption. Brands with proven durability and positive user feedback were favored. The ranking reflects a combination of initial cost, ongoing maintenance, and suitability for different household sizes and fuel types, helping buyers find the best fit for their specific situations.Factors to Consider When Choosing Best Tankless Water Heaters
Choosing the best tankless water heater depends on several key factors. Beyond initial price, buyers should consider capacity, energy efficiency, installation requirements, and fuel type. Making an informed decision involves understanding how each feature impacts daily use, long-term costs, and compatibility with your home. Here are the main factors to keep in mind when selecting a tankless water heater.Capacity and Flow Rate
Capacity, measured in gallons per minute (GPM), determines how many fixtures can simultaneously draw hot water. Larger households or homes with multiple bathrooms typically need higher GPM units, while smaller homes or point-of-use applications may suffice with lower flow rates. Choosing a unit with insufficient capacity results in cold water during peak usage, so assessing your household’s hot water demand is essential before buying.
Fuel Type and Efficiency
Tankless water heaters are available in electric, natural gas, and propane models. Gas units generally provide higher flow rates and are better suited for larger homes, but they require venting and more complex installation. Electric models tend to be simpler and cheaper to install but may have limited capacity. Efficiency ratings, especially for gas models, matter because they influence ongoing energy costs—condensing models often offer better efficiency than non-condensing ones.
Installation and Space Requirements
Some units are compact and designed for easy installation in tight spaces, making them ideal for retrofits or small homes. Others, especially high-capacity gas models, may need dedicated venting and professional setup, increasing overall costs. Evaluate your available space and whether your home’s existing infrastructure supports the unit’s installation requirements to avoid surprises later.
Temperature Control and Features
Features like digital displays, Wi-Fi controls, and temperature memory enhance usability and allow for precise temperature settings. However, these features often come with higher price tags. Consider whether smart controls or advanced interfaces add value for your household’s convenience or if a basic model will meet your needs without extra cost.
Cost and Long-Term Value
Initial purchase price varies widely, from budget electric units to premium gas models. While cheaper units may seem appealing upfront, they could lead to higher energy bills or more frequent maintenance. Balancing initial costs with long-term savings and durability ensures you select a unit that provides value over its lifespan, especially if you plan to live in your home for many years.
Frequently Asked Questions
Can I install a tankless water heater myself?
While some electric models are designed for simple installation and might be manageable for experienced DIYers, most gas units and higher-capacity electric models require professional installation. Proper setup involves ensuring correct venting, gas connections, and electrical wiring, which are critical for safety and performance. Hiring a licensed technician not only ensures compliance with local codes but also helps avoid costly mistakes and potential hazards.
How do I know what size tankless water heater I need?
Determining the right size depends on your household’s hot water demand. Calculate the GPM needed for your most used fixtures—such as showers, faucets, and appliances—during peak times. A unit with too low a flow rate will struggle to supply multiple fixtures simultaneously, leading to cold water. Conversely, oversizing can lead to unnecessary energy costs. Reviewing your household’s typical usage patterns helps pick a unit that balances capacity and efficiency.
Are condensing gas models worth the extra cost?
Condensing gas water heaters are generally more efficient than standard models, translating into lower energy bills over time. They recover more heat from exhaust gases, making them a smart choice for energy-conscious buyers. However, they tend to have higher upfront costs and more complex installation requirements. If long-term savings and environmental impact matter, investing in a condensing model can be worthwhile, but verify that your home infrastructure supports its installation.
What maintenance do tankless water heaters require?
Most tankless units require regular descaling, especially in areas with hard water, to prevent mineral buildup that can impair performance. Checking the manufacturer’s guidelines for annual maintenance is advised. Additionally, inspecting filters and flush valves ensures the unit continues operating efficiently. Proper maintenance extends the lifespan of your heater and maintains its energy efficiency, ultimately saving you money and hassle.
Is it better to choose a higher GPM unit for future proofing?
Opting for a unit with a higher GPM than your current needs can accommodate future expansion or increased hot water demand. However, higher-capacity models often come with increased costs and energy consumption. If your household is likely to grow or you plan to add more fixtures, investing in a slightly larger unit makes sense. Otherwise, selecting a model aligned with your current usage helps avoid unnecessary expenditure.
Conclusion
For most households, the Rinnai RX199iN offers the best balance of capacity, efficiency, and smart features, making it the top overall choice. Budget-conscious buyers or small homes will find the EcoSmart ECO 11 an excellent value, especially for point-of-use applications. For those seeking premium performance and the highest GPM, the NEW Rinnai RX199iN or Rheem RX199iN are ideal. Beginners or those replacing an aging unit should consider electric models like the Stiebel Eltron Tempra 29 Plus for straightforward installation. Ultimately, your selection depends on household size, fuel preferences, and budget—match your needs to these recommendations for reliable hot water in 2026.
