Tankless water heaters offer on-demand hot water, saving space and energy compared to traditional tanks. The best models balance performance, efficiency, and ease of installation, but tradeoffs exist. The Rinnai RX160iN stands out as the top overall pick for reliability and smart features, while the APUS 27kW Electric Heater offers excellent flow rates for larger households. Cheaper models may sacrifice durability or performance, whereas premium units can be costly but deliver unmatched versatility. Continue reading for a full breakdown of the best options and what to consider before buying.
Key Takeaways
- Electric models dominate for small to medium households due to easier installation and lower upfront costs.
- Gas-powered units like the Rinnai RX160iN excel in high flow rates and larger household applications but are more complex to install.
- Performance varies significantly based on incoming water temperature; colder climates require more powerful units.
- Smart features and WiFi connectivity are increasingly common in premium models for remote monitoring and control.
- Choosing the right size and power capacity is critical to avoid insufficient hot water or excessive energy use.
| tankless water heater | Voltage | Flow Rate | Power | Maximum Temperature |
|---|---|---|---|---|
| Stiebel Eltron Tempra 24 Trend | 240V | — | 24kW | — |
| APUS 27kW Electric Tankless Wa | 240V | 6.5 GPM | 27,000 watts | 140°F |
| 110V Electric Tankless Water H | 110V | 0.5 GPM at 35°F increase | 3000W | — |
| 14kW Tankless Electric Water H | 240V | 3.3 GPM | 14kW | 131°F |
| 110V Tankless Electric Water H | 110V | 0.3-0.5 GPM | 3000W | 131°F |
| 14kW Tankless Electric Water H | 240 volts | 3.38 GPM | — | 140 °F |
| Rheem 8kW Multi Fixture Tankle | 240V | up to 1.95 GPM | 8kW | — |
| Rinnai RX160iN Condensing Smar | — | 9 GPM | — | — |
| 110V Tankless Electric Water H | 110V | 0.45 gpm | — | 131 °F |
| Tankless Electric Water Heater | 110V | — | 3000W | — |
| Rheem RTG Series 7.0 GPM Natur | — | 7.0 GPM | — | — |
| 18kW Electric Tankless Water H | 240 volts | 4.3 gpm | — | 140 °F |
More Details on Our Top Picks
Stiebel Eltron Tempra 24 Trend Electric Tankless Water Heater, 24kW, 240V
The Stiebel Eltron Tempra 24 Trend stands out for its energy-efficient self-modulating technology that adapts power use based on demand, making it a smart choice for households with up to two showers in warm climates. Compared with larger units like the Rinnai RX160iN, it offers a compact design that saves space but delivers less capacity, limiting its suitability for bigger households or colder environments. Its digital temperature display allows precise control, yet the need for a hefty 150 A electrical service can pose installation challenges. This model is ideal for those seeking a reliable, space-saving solution with good energy management, but it’s less suited for larger homes that demand higher flow rates or colder climates. Requires high electrical capacity, which may incur additional costs or upgrades.
Pros:- Provides continuous hot water on demand
- Energy-efficient with auto-modulation technology
- Compact space-saving design
- Digital temperature display for easy control
Cons:- Requires a high electrical service of 150 A
- Limited output for larger households or in cooler climates
Best for: Small households or apartments in warm climates needing efficient on-demand hot water for 1-2 points of use
Not ideal for: Large families or homes in cold regions where higher flow rates and capacity are necessary
- Power:24kW
- Voltage:240V
- Recommended Electric Service:150 A
- Output Water Temperature:68°F to 140°F
Our verdict“This model is best for small, energy-conscious households in warm areas seeking reliable, space-efficient hot water.”
APUS 27kW Electric Tankless Water Heater, 240V, Up to 6.5 GPM, Instant
The APUS 27kW Electric Tankless Water Heater makes a compelling case for families needing simultaneous hot water at multiple fixtures, thanks to its impressive 6.5 GPM flow rate. Unlike the smaller Tempra, it supports higher demand but demands professional installation due to its substantial electrical requirements—specifically a dedicated 240V circuit with three 40-amp breakers. Its compact wall-mounted design saves space, and its digital control offers precise temperature adjustment, setting it apart from less powerful models like the 14kW unit. The main tradeoff is the need for a robust electrical setup, which can increase upfront costs and complexity. It’s an excellent choice for larger households or those with multiple bathrooms, but not suitable for renters or small homes without electrical upgrades.
Pros:- Supports multiple simultaneous fixtures
- Digital temperature control for precision
- Space-efficient wall-mount design
- Self-modulating technology enhances efficiency
Cons:- Requires professional installation due to electrical demands
- Flow rate may vary with inlet water temperature
Best for: Families or shared households with multiple bathrooms needing simultaneous hot water
Not ideal for: Renters or small homes without the electrical capacity for dedicated circuits
- Power:27,000 watts
- Voltage:240V
- Flow Rate:6.5 GPM
- Maximum Temperature:140°F
- Dimensions:11.42″ W x 17.72″ H x 3.54″ D
- Weight:19 pounds
Our verdict“This unit is ideal for larger households with high hot water demand and existing electrical capacity.”
110V Electric Tankless Water Heater, 3000W
The 110V Electric Tankless Water Heater offers quick hot water for small-scale needs, such as kitchen sinks or RV bathrooms. Its compact stainless steel and ABS construction makes it highly portable and easy to install, especially for spaces where installing high-capacity units isn’t feasible. Compared to the 14kW model, it has a lower power output, which limits flow rate and hot water volume but makes it easier to connect to standard household circuits. The LED display and safety features like leak detection and dry-boil prevention improve reliability and user control. However, it isn’t suitable for shower applications or high-demand scenarios, and its flow rate is limited, making it less adaptable for larger households or multiple fixtures.
Pros:- Compact and portable design
- Fast heating with real-time LED display
- Multiple safety features for reliable operation
- Easy to install with standard connections
Cons:- Limited flow rate for high-demand uses
- Not suitable for shower applications
Best for: RVs, small apartments, or single-point applications like kitchen sinks
Not ideal for: Large households or shower setups requiring higher flow rates
- Power:3000W
- Voltage:110V
- Flow Rate:0.5 GPM at 35°F increase
- Material:Stainless steel and ABS
- Safety Features:IPX4 waterproofing, leak detection, dry-boil prevention
Our verdict“This heater is best for small spaces or single-use points where space and simplicity matter most.”
14kW Tankless Electric Water Heater 240V for Sink & Shower, Gray
The 14kW Tankless Electric Water Heater offers an affordable, space-efficient solution for providing hot water at individual points like sinks or small bathrooms. It supports up to 3.3 GPM, making it suitable for a single fixture or a small household. Its smart temperature control and safety features, including overheat and leakage protections, add reliability over basic models. Compared with the 27kW unit, it’s less powerful but easier to install for most DIYers or those with existing 240V circuits. However, its limited flow rate restricts it to small demand applications, and it’s not designed for multiple simultaneous fixtures or high-demand shower use. It’s an excellent fit for quick, targeted hot water needs in tight spaces.
Pros:- Space-saving and easy to install
- Supports up to 3.3 GPM for small applications
- Smart temperature controls with safety protections
- Affordable compared to larger units
Cons:- Limited flow rate restricts multi-point use
- Not suitable for high-demand shower applications
Best for: Homeowners needing point-of-use hot water for sinks or small bathrooms
Not ideal for: Large families or households with multiple bathrooms requiring simultaneous hot water
- Power:14kW
- Voltage:240V
- Flow Rate:3.3 GPM
- Maximum Temperature:131°F
- Mount Type:Wall
- Dimensions:12.2″ W x 17.25″ H
Our verdict“This heater works best for targeted, small-scale hot water needs in tight spaces or single fixtures.”
110V Tankless Electric Water Heater, 3000W, Instant Hot Water with Digital Display for Kitchen and Bathroom
The 110V Tankless Electric Water Heater is tailored for small-scale, space-constrained applications like RVs, small kitchens, or bathrooms. Its tiny footprint and wall-mounted design make it incredibly easy to install in tight spots, and its 3000W power supports instant hot water with a 0.3-0.5 GPM flow rate—ideal for quick tasks but not for showering or multiple fixtures. Compared to the 14kW unit, it offers a similar flow rate but with a more portable form factor, making it perfect for temporary setups or secondary points of use. The multiple safety protections and waterproofing add peace of mind, though its limited flow restricts high-demand uses. It’s best suited for travelers or tiny homes needing reliable, immediate hot water at a single point.
Pros:- Extremely compact and portable
- Supports instant hot water at small flow rates
- Safety protections and waterproof design
- Easy to install with standard connections
Cons:- Limited flow rate unsuitable for showers
- Vertical installation only, no horizontal option
Best for: RVs, tiny homes, or small single-point applications needing instant hot water
Not ideal for: Homes with high hot water demand or multiple fixtures running simultaneously
- Power:3000W
- Voltage:110V
- Maximum Temperature:131°F
- Flow Rate:0.3-0.5 GPM
- Safety Features:Leakage, dry-boil, overheating protection
- Certifications:ETL
Our verdict“Ideal for travelers or tiny-home dwellers seeking quick, reliable hot water in small spaces.”
14kW Tankless Electric Water Heater, On Demand, 240V, 3.38 GPM
This 14kW unit stands out for its ability to deliver instant hot water to 2-3 fixtures simultaneously, making it a strong choice for small households or secondary points of use. Compared with the Rheem 8kW model, it offers a higher flow rate and more capacity, but it requires a dedicated 60A circuit, which can complicate installation for some users. Its space-saving design and efficiency make it ideal for installations where room is limited and energy savings matter most. However, the maximum temperature of 140°F may limit its use in certain applications, and its complex wiring needs could deter DIYers.
Pros:- Provides instant, endless hot water for multiple outlets
- High efficiency with up to 60% energy savings
- Compact, space-saving design for easy installation
Cons:- Requires a dedicated 60A circuit breaker and proper wiring
- Installation can be complex for non-professionals
- Limited maximum temperature of 140°F
Best for: Homeowners needing a compact, high-capacity electric heater for multiple points of use in small spaces.
Not ideal for: Those with existing limited electrical capacity or who prefer simple plug-and-play units for single fixtures.
- Power Source:Hard Wiring Required
- Wattage:14 KW
- Voltage:240 volts
- Maximum Temperature:140 °F
- Flow Rate:3.38 GPM
- Dimensions:9.5″W x 14.2″H x 3.1″D
Our verdict“This model suits small households or secondary points where space and efficiency are priorities, but requires careful electrical planning.”
Rheem 8kW Multi Fixture Tankless Electric Water Heater – 240V
The Rheem 8kW unit offers a practical solution for households that need hot water at a single fixture or small number of fixtures, with its digital thermostatic controls providing precise temperature settings. Compared with the higher-capacity 14kW heater, it has a lower flow rate of up to 1.95 GPM, making it less suitable for simultaneous multiple fixtures but ideal for point-of-use scenarios. Its compact design and energy-efficient operation make it appealing for small homes or renovation projects. However, it requires professional installation and specific electrical wiring, limiting DIY potential, and its flow rate may fall short for larger households with multiple simultaneous demands.
Pros:- Space-saving, compact size
- Energy-efficient operation by heating only when needed
- Digital controls for precise temperature adjustment
Cons:- Requires professional installation and proper electrical wiring
- Limited flow rate may not support multiple fixtures at once
- Only suitable for single-phase power systems
Best for: Individuals or small families seeking a reliable, energy-efficient hot water solution for single fixtures or low-demand setups.
Not ideal for: High-demand households or those looking for a multi-point heater capable of supporting several fixtures simultaneously.
- Power:8kW
- Voltage:240V
- Flow Rate:up to 1.95 GPM
- Temperature Range:80°F – 140°F
- Warranty:5-Year Leak, 1-Year Parts
Our verdict“Ideal for low-demand applications where space and energy savings are more important than high flow capacity.”
Rinnai RX160iN Condensing Smart Sense Tankless Water Heater
The Rinnai RX160iN combines high flow capacity—up to 9 GPM—with advanced features like Wi-Fi connectivity, making it suitable for larger households or commercial use. Its condensing design offers excellent energy efficiency with a UEF of .97, surpassing most electric models in operational savings. Compared to the electric Rheem or smaller electric units, this gas-powered heater provides consistent hot water at multiple fixtures simultaneously, but it requires professional installation and proper venting, which can add to the overall cost. Its smart controls and outdoor/indoor flexibility make it a versatile choice for those seeking a durable, energy-efficient system with remote management capabilities.
Pros:- High flow rate supports multiple fixtures simultaneously
- Excellent energy efficiency with UEF .97
- Supports Wi-Fi control for remote operation
Cons:- Requires professional installation, including venting
- Separate Control-R module needed for Wi-Fi
- Outdoor installation requires Versa Vent
Best for: Larger households or small commercial spaces needing high flow rates and smart control features.
Not ideal for: Small homes or users preferring electric units with simple installation and lower upfront costs.
- Flow Rate:9 GPM
- Fuel Type:Propane or Natural Gas
- Efficiency:UEF .97
- Installation Options:Indoor or Outdoor
- Warranty:15-year on heat exchanger
Our verdict“This unit appeals to those demanding high capacity and smart features, but with a higher installation complexity and cost.”
110V Tankless Electric Water Heater, 3000W, Instant Hot Water with Digital Display for Kitchen and More
This 110V unit is tailored for small-scale applications such as kitchen sinks, RVs, or outdoor setups, offering instant hot water with precise digital temperature control. Compared with larger electric models like the 14kW heater, it provides a modest flow rate of 0.45 GPM, making it unsuitable for shower use and high-demand scenarios. Its compact size and straightforward installation appeal to DIYers and those limited by space or electrical capacity. Safety features like waterproofing and overheat protection enhance reliability, but the limited flow rate restricts its use to low-volume needs such as handwashing or small appliances.
Pros:- Instant water heating with precise temp control
- Compact, wall-mounted design
- Safety features including waterproofing and overheat protection
Cons:- Not suitable for shower use
- Limited flow rate restricts high-demand applications
- Horizontal installation not permitted
Best for: RVers, outdoor enthusiasts, or kitchen applications requiring instant, small-volume hot water.
Not ideal for: High-demand households or showering needs, due to limited flow rate and temperature range.
- Power Source:AC
- Wattage:3000W
- Voltage:110V
- Maximum Temperature:131 °F
- Flow Rate:0.45 gpm
- Warranty:24 months
Our verdict“A smart choice for small-scale, low-flow needs in tight spaces, but not for whole-house or high-demand use.”
Tankless Electric Water Heater, 3000W, 110V, Digital Display, Compact & Wall-Mountable
This 3000W unit is designed for minimal space applications like small kitchens or RVs, with a wall-mountable, compact form factor and easy-to-read digital display. It matches the flow rate of the 110V heater by supporting between 0.3 to 0.5 GPM, making it suitable for low-volume tasks. Compared with the 14kW electric heater, it offers fewer features and lower capacity but benefits from simpler wiring and a lower price point. Its safety protections and straightforward installation make it accessible for DIY setups, though it cannot support high-demand or multiple fixture use.
Pros:- Compact, space-saving design
- Instant hot water with digital control
- Easy to install with standard wiring
Cons:- Limited flow rate restricts use to low-demand scenarios
- Not suitable for shower use
- Requires specific wiring and breaker capacity
Best for: Budget-conscious users needing a space-efficient, low-flow water heater for small applications.
Not ideal for: High-demand or multi-use households, or those needing hot water for showers or multiple fixtures simultaneously.
- Power:3000W
- Voltage:110V
- Temperature Rise:82°F to 131°F
- Water Flow Rate:0.3GPM to 0.5GPM
- Protection Features:IPX4 waterproof, leakage, dry-burning, over-temp
Our verdict“A practical, affordable choice for low-volume hot water needs where space and budget are limited, but not for large or high-demand applications.”
Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater Indoor
The Rheem RTG Series stands out as the best overall choice for large households needing reliable, continuous hot water across multiple fixtures. Its 7.0 GPM flow rate ensures ample hot water supply, even during simultaneous use in a multi-bathroom home. Compared to electric options like the 18kW Electric Tankless Water Heater, this gas model delivers higher throughput, making it ideal for bigger households. The integrated safety features and CSA certification provide peace of mind, although the need for venting and higher initial investment can be drawbacks. Its space-saving wall-mount design makes it suitable for indoor installation in utility closets or basements. Overall, this model balances capacity, efficiency, and safety for those with larger hot water demands, despite the added complexity of venting.
Pros:- Provides endless hot water for multiple outlets simultaneously
- High energy efficiency with significant cost savings over time
- Space-saving wall-mount installation
Cons:- Requires indoor installation and venting, increasing setup complexity
- Higher upfront cost compared to traditional tank heaters
Best for: Large families or multi-bathroom homes that require high flow rates and continuous hot water supply.
Not ideal for: Small households or apartments where space is limited and low-cost electric options suffice.
- Flow Rate:7.0 GPM
- BTU:160,000 BTUs
- Energy Factor:0.82 UEF
- Installation Type:Indoor
- Safety Certifications:CSA Certified
Our verdict“This model is best suited for large households needing reliable, high-capacity hot water with safety and efficiency in mind.”
18kW Electric Tankless Water Heater 240V WiFi Certified
The 18kW Electric Tankless Water Heater is a strong choice for small households or those prioritizing space efficiency. Its compact dimensions and wall-mounted design make it easy to install in tight spaces, surpassing bulkier electric models in convenience. Compared to the gas-powered Rheem RTG, this unit offers instant hot water without venting or fuel considerations, but its 4.3 GPM flow rate limits its suitability for larger households or simultaneous high-demand fixtures. The WiFi control and smart features add modern convenience, though professional electrical installation and a dedicated circuit are necessary—an important consideration for less experienced DIYers. This heater excels in mild climates and smaller setups, especially where space and quick installation matter most.
Pros:- Provides continuous hot water without preheating delays
- Space-saving, wall-mounted, and lightweight design
- Energy-efficient with self-modulating technology
Cons:- Requires professional electrical setup and dedicated circuit
- Limited flow rate may not meet high-demand needs in larger households
- Best suited for mild to moderate climate conditions
Best for: Small households, singles, or apartments needing reliable hot water with minimal space requirements and smart controls.
Not ideal for: Large families or homes with multiple bathrooms demanding higher flow rates or more simultaneous outlets.
- Power Source:AC
- Wattage:18,000 watts
- Voltage:240 volts
- Flow Rate:4.3 gpm
- Maximum Temperature:140 °F
- Certifications:ETL Certified
Our verdict“This electric unit makes the most sense for small homes or apartments prioritizing space, safety, and smart features, rather than high-volume use.”
How We Picked
This lineup was assembled by evaluating each unit’s heating capacity, flow rate, build quality, ease of installation, and user features. I prioritized models that balance performance with value, ensuring they suit various household sizes and budgets. The ranking favors units with proven reliability, positive customer feedback, and features that enhance usability. Consideration was also given to energy efficiency and maintenance requirements, helping buyers identify options that will deliver consistent performance over time.Factors to Consider When Choosing Tankless Water Heaters
Selecting the right tankless water heater involves weighing several important factors. Beyond initial cost, buyers should consider the unit’s capacity, energy source, and compatibility with their household’s hot water demands. Proper sizing prevents issues like insufficient hot water or wasted energy. Installation complexity and ongoing maintenance also influence long-term satisfaction. Understanding these factors ensures a choice that balances performance, affordability, and convenience.Flow Rate and Capacity
The primary consideration is whether the heater can deliver enough hot water for your household. Flow rate, measured in gallons per minute (GPM), determines how many fixtures can operate simultaneously without losing temperature. Larger households with multiple bathrooms need higher GPM units, often above 7 GPM, while singles or couples can get by with lower capacity models. Misjudging this can result in cold water during busy mornings or when multiple appliances run at once.
Energy Source: Electric vs. Gas
Electric tankless heaters are generally easier to install and less expensive upfront, making them ideal for smaller homes or point-of-use applications. Gas models, however, can provide higher flow rates and are better suited for large households or whole-home solutions, especially in colder climates where water temperature drops significantly. The tradeoff is that gas units often require venting and more complex installation, which adds to the cost and complexity.
Size and Space Requirements
Tankless water heaters vary greatly in size. Compact models are perfect for small spaces like under sinks or in closets, while larger units designed for whole-home use may need more room and proper venting. Buyers should measure their installation area carefully and consider future needs—opting for a slightly larger unit can prevent upgrades later, but oversized units may consume unnecessary energy and cost more initially.
Energy Efficiency and Operating Costs
Energy efficiency impacts ongoing costs significantly. Look for units with high energy factors (EF) or uniform energy factors (UEF), which indicate better efficiency. Features like condensing technology in gas models can boost efficiency but often come with higher upfront costs. Electric models tend to be simpler but may struggle in colder climates unless they are rated for such conditions. Calculating long-term savings versus initial investment is key.
Ease of Installation and Maintenance
Some units are plug-and-play, suitable for DIY installation, while others require professional setup, especially gas models. Maintenance needs vary—electric units typically require minimal upkeep, but regular descaling may be needed in hard water areas. Gas units may need periodic vent cleaning and more complex servicing. Considering your comfort with installation and maintenance tasks can prevent future headaches and costs.
Frequently Asked Questions
Can I install a tankless water heater myself?
For electric tankless water heaters, some models are designed for DIY installation if you have basic electrical skills and tools, but many require professional wiring. Gas units generally demand a licensed plumber and proper venting, making DIY installation inadvisable. Incorrect installation can lead to safety hazards, poor performance, or damage, so assess your skills carefully before attempting installation yourself.
How long do tankless water heaters last?
Most tankless water heaters last between 20 to 25 years with proper maintenance, which is longer than traditional tank models. Regular descaling and servicing help extend their lifespan, especially in areas with hard water. Investing in a reputable brand and adhering to maintenance schedules can maximize your unit’s longevity and performance.
Will a tankless water heater work well in cold climates?
In colder regions, incoming water temperature can significantly impact performance. You may need a higher capacity unit or a model with enhanced heating power. Proper insulation and correct sizing are essential to ensure consistent hot water supply during winter months. Some models are specifically designed to perform well in low-temperature environments, making them a better fit for such conditions.
Are electric tankless water heaters suitable for whole-house use?
Electric models can handle whole-house applications but are typically limited to smaller households or areas with moderate hot water needs due to their lower flow capacity. They are ideal for point-of-use applications or small homes where space and simplicity matter. For larger households or high-demand scenarios, gas-powered or higher-capacity electric models are usually more appropriate.
What’s the main difference between condensing and non-condensing gas units?
Condensing gas units are more efficient because they recover more heat from exhaust gases, saving energy and reducing operating costs. They often cost more upfront but pay off over time with lower energy bills. Non-condensing units are simpler and cheaper initially but tend to be less efficient, making them suitable for applications where budget constraints outweigh long-term savings.
Conclusion
For those seeking the best overall experience, the Rinnai RX160iN offers reliable performance and smart features suitable for most households. Budget-conscious buyers should consider electric models like the APUS 27kW for their affordability and ease of installation. For larger homes or colder climates, gas units such as the Rheem RTG Series provide higher flow rates and efficient operation. Beginners or those with limited space will benefit from compact, point-of-use models, while homeowners wanting long-term savings might prioritize units with advanced efficiency features. Ultimately, selecting the right tankless water heater depends on your household size, climate, and budget—use this guide to find your perfect match.
