Tankless water heaters are a popular choice for those seeking on-demand hot water without the bulk of traditional tanks. The best options balance energy efficiency, installation flexibility, and cost, but they vary significantly in performance and features. The Rinnai RE160eP stands out as the overall best for its reliability and high flow rate, while the APUS 14kW Electric Heater offers excellent space-saving design for smaller homes or apartments. Buyers often face tradeoffs between gas versus electric models, upfront costs versus long-term savings, and flow rate capacity versus size. Keep reading to see how these models compare and which one might suit your needs best.
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Key Takeaways
- Gas-powered models like Rinnai provide higher flow rates suitable for larger households, but come with higher installation complexity and cost.
- Electric tankless heaters are more compact and easier to install, ideal for small spaces or secondary applications, but generally have lower flow capacities.
- Flow rate capacity is a key differentiator; selecting a unit that matches your household’s hot water demand prevents shortages.
- Space-saving and outdoor models expand installation options but may have limitations in capacity or require weatherproofing.
- Price varies widely; investing in a higher-capacity or premium model can reduce operational costs and improve longevity.
| tankless water heater | Flow Rate |
|---|---|
| Rheem 18kW 240V Tankless Elect | up to 4.4 GPM |
| Rheem 11kW 240V Tankless Elect | up to 2.68 GPM |
| APUS 14kW Tankless Electric Wa | 3.3 GPM |
| Camplux Climatech 5 Tankless G | 6.86 GPM |
| Rinnai RE160eP Non-Condensing | 6.1 GPM |
| Rinnai REP160eN Smart-Circ Non | Up to 6.6 GPM |
| APUS Propane Tankless Water He | 5.43 GPM |
More Details on Our Top Picks
Rheem 18kW 240V Tankless Electric Water Heater, Gray
This Rheem model stands out for its high flow rate of up to 4.4 GPM, making it suitable for small to medium households needing reliable hot water. Its precise digital thermostat with LED display allows for accurate temperature adjustments, a feature that surpasses the simpler controls of the Rheem 11kW model. The copper heating elements contribute to durability, but the 18kW power requirement means it needs a robust 240V supply, which could involve electrical upgrades. Compared to the APUS 14kW unit, it offers a higher flow rate but at the cost of greater installation complexity. This pick makes the most sense for homeowners with moderate hot water needs who can handle the electrical setup. However, it may be overkill for small apartments or single fixtures. Its pros include a high flow rate, precise digital controls, and durable copper elements. Drawbacks include the need for a 240V power source and potential plumbing adjustments during install. Overall, it’s a flexible choice for those who want dependable performance with detailed temperature management.Pros:- Precise digital temperature control with LED display
- High flow rate of up to 4.4 GPM
- Durable copper heating elements
Cons:- Requires a 240V power supply, which may need electrical upgrades
- Installation may require plumbing adjustments
Best for: Small to medium households needing reliable, adjustable hot water without space constraints
Not ideal for: Homes with limited electrical capacity or very small spaces where power upgrades are unfeasible
- Power:18kW
- Voltage:240V
- Flow Rate:up to 4.4 GPM
- Color:Gray
- Heating Elements:Copper immersion, field serviceable
- Installation:Bottom 3/4 inch NPT water connections
Our verdict“This model is ideal for households seeking consistent hot water with precise temperature control and sufficient flow rate, provided electrical capacity is adequate.”
Rheem 11kW 240V Tankless Electric Water Heater
The Rheem 11kW unit offers a smaller capacity, providing up to 2.68 GPM, which makes it suitable for single fixtures or small apartments. Its self-modulating control and adjustable digital temperature display enhance efficiency compared to traditional on/off models like the APUS 14kW. However, its limited flow rate means it won’t support multiple simultaneous outlets in larger households. Compared to the 18kW Rheem, it’s less powerful but easier to install in spaces with limited electrical capacity. This makes it a strong choice for budget-conscious buyers needing reliable hot water for a single sink or shower. The main tradeoffs are its lower flow rate and the requirement for a 240V circuit upgrade, similar to other electric models. Its pros include efficiency features, digital temperature control, and a compact size. Its cons are the limited flow and potential electrical upgrade needs. Overall, it’s best for small households or individual use where budget and space are limited.Pros:- Adjustable digital temperature display
- Self-modulating power control for efficiency
- Provides continuous hot water on demand
Cons:- Limited flow rate of 2.68 GPM may not serve multiple fixtures
- Requires 240V power supply, possibly needing electrical upgrades
Best for: Singles or couples living in small apartments with modest hot water needs
Not ideal for: Large families or homes with multiple bathrooms requiring simultaneous hot water
- Power:11kW
- Voltage:240V
- Flow Rate:up to 2.68 GPM
- Water Connections:1/2″ NPT
Our verdict“This unit suits small households or single fixtures well, especially where budget and electrical capacity are considerations.”
APUS 14kW Tankless Electric Water Heater, 240V, 3.3 GPM, LED Display, Space-Saving
This ultra-slim, wall-mounted unit excels in tight spaces, making it ideal for apartments or small utility areas. Its 3.3 GPM flow rate is adequate for single fixtures or small sinks but limits its effectiveness for simultaneous multiple uses. The LED display allows for precise temperature adjustment, and its high energy efficiency of 99.8% helps reduce operating costs. Compared with larger models like the Rheem 18kW, it sacrifices flow capacity for space savings and ease of installation. The unit requires a dedicated 60A breaker and specific wiring, meaning professional setup is necessary. Its safety features and anti-leak protections add peace of mind, but the installation complexity could be a barrier for DIYers. The pros include space efficiency, high thermal efficiency, and safety features; the main drawbacks are flow limitations and installation requirements. This pick makes sense for those prioritizing space and efficiency over high flow capacity.Pros:- Space-saving wall-mounted design
- High energy efficiency of 99.8%
- LED digital display for precise temperature control
- Built-in safety protections and anti-leakage features
Cons:- Requires a 60A breaker and specific wiring
- Limited flow rate may not support multiple fixtures simultaneously
Best for: Small apartments or condos with limited space needing reliable hot water for one or two fixtures
Not ideal for: Large households or homes needing simultaneous hot water outlets
- Power:14kW
- Voltage:240V
- Flow Rate:3.3 GPM
- Dimensions:13.7″ × 11.42″ × 3.54″
- Temperature Range:86°F–131°F
- Connections:3/4″ NPT
Our verdict“This compact unit is perfect for space-constrained settings where dependable hot water for a single fixture is needed without sacrificing efficiency.”
Camplux Climatech 5 Tankless Gas Water Heater, Outdoor, 6.86 GPM, 199,000 BTU
This gas-powered outdoor heater offers a substantial flow rate of up to 6.86 GPM, making it suitable for whole-house applications or large families. Its 199,000 BTU output surpasses many electric models, providing rapid hot water even under colder inlet conditions. Compared with electric options like the Rheem 11kW, it handles higher volumes and can serve multiple fixtures at once. The CSA certification and multiple safety protections—such as anti-freezing and flame failure—add confidence for outdoor use. Its main tradeoff is the need for outdoor space and a natural gas connection, which limits flexibility for indoor installations. Additionally, performance depends heavily on inlet water temperature, so colder climates may see reduced flow. Pros include high flow rate, outdoor installation suitability, and safety features. Drawbacks involve space requirements and gas dependency. It’s best for larger households or outdoor setups where electric units might fall short.Pros:- High flow rate of 6.86 GPM supports whole-house use
- CSA certified for safety and quality
- Space-saving outdoor installation
- Multiple safety protections
Cons:- Requires outdoor installation space
- Limited to natural gas supply
- Performance varies with inlet water temperature
Best for: Homeowners with outdoor space needing a reliable, high-capacity hot water source for multiple fixtures
Not ideal for: Indoor use or homes without access to natural gas supply
- Flow Rate:6.86 GPM
- Maximum Flow Rate:8.4 GPM
- BTU:199,000
- Certification:CSA Certified
- Installation:Outdoor
- Protection Features:Anti-Freezing, Dry Combustion, Overheat, High Water Pressure, Low Water Flow, Flame Failure
Our verdict“This outdoor gas heater excels for large households needing high-volume hot water in outdoor spaces, with safety and efficiency features built-in.”
Rinnai RE160eP Non-Condensing Propane Tankless Water Heater, Up to 6.1 GPM, Outdoor Installation, 160,000 BTU
The Rinnai RE160eP offers a balanced approach for outdoor propane hot water needs, delivering up to 6.1 GPM to support multiple fixtures. Its non-condensing design prioritizes durability and efficiency, with a long 15-year warranty on the heat exchanger and a 5-year on parts. Compared to the gas-powered Camplux, it provides similar flow but is generally more suited for residential settings with existing propane connections. Its LED service reminder system and error codes aid maintenance, but WiFi control isn’t included, which may be a drawback for tech-savvy users. The unit’s outdoor installation requirement and dependency on propane make it less flexible than electric models for indoor use or electric-only homes. Its main strengths lie in energy efficiency, warranty coverage, and size, while the main tradeoffs involve installation and control features. It’s ideal for outdoor households relying on propane and seeking long-term reliability.Pros:- Energy-efficient design heats water only when needed
- Compact size suitable for outdoor installation
- LED screen for service reminders and error codes
- Long warranty coverage for durability
Cons:- Professional installation recommended
- WiFi control module not included
- Dependent on outdoor space and propane supply
Best for: Outdoor homeowners with propane access needing reliable, high-capacity hot water for multiple fixtures
Not ideal for: Indoor spaces without outdoor installation options or electric-only homes
- Flow Rate:6.1 GPM
- BTU:160,000
- Installation Type:Outdoor
- Warranty:15-year on heat exchanger, 5-year on parts and labor
Our verdict“This propane outdoor heater is a solid choice for long-term, high-volume hot water in outdoor settings with propane access.”
Rinnai REP160eN Smart-Circ Non-Condensing Natural Gas Tankless Water Heater, 160,000 BTU, Outdoor, Up to 6.6 GPM
The Rinnai REP160eN stands out for its Smart-Circ technology, which adapts to your water usage, making it highly energy-efficient compared to traditional models. Its outdoor design means no indoor space is needed, and the high flow rate of 6.6 GPM makes it suitable for households with multiple fixtures. Unlike the APUS Propane heater, which offers slightly lower flow and capacity, this model’s learning feature reduces waste and operating costs over time. However, professional installation is recommended due to gas and venting requirements, and the WiFi control isn’t included by default, which could limit smart-home integration. The 15-year warranty on the heat exchanger provides peace of mind, but registration within 90 days is necessary to activate it. Overall, this heater suits owners seeking a reliable, tech-savvy outdoor solution with high capacity.
Pros:- Smart-Circ technology learns water usage, reducing energy waste
- Compact outdoor design saves indoor space
- High flow rate supports multiple fixtures simultaneously
- Long warranty offers peace of mind
Cons:- Requires professional installation, adding to upfront costs
- WiFi control module not included by default
- Limited warranty registration window may be inconvenient
Best for: Homeowners wanting an energy-efficient, outdoor gas heater with smart features and high flow capacity.
Not ideal for: DIY enthusiasts or those with limited outdoor space, since installation is complex and requires professional help.
- BTU:160,000
- Flow Rate:Up to 6.6 GPM
- Installation:Outdoor
- Recirculation Pump:Built-in
- Warranty:15-year on heat exchanger, 5-year on parts and labor
- WiFi Control:Not included
Our verdict“This model is ideal for users seeking a smart, outdoor gas heater with high capacity and long-term reliability.”
APUS Propane Tankless Water Heater, 120,000 BTU, 5.5 GPM, Indoor Hot Water Heater with Digital Display, Space Gray
The APUS Propane Tankless Water Heater excels for its precise digital controls and quiet operation, making it a solid choice for indoor spaces. Its 120,000 BTU heating capacity and 5.5 GPM flow rate are well suited for medium-sized households, especially when compared to the lower capacities of models like the Rheem 11kW electric heater. The digital display provides accurate temperature adjustments, which is a step up from basic models and helps avoid scalding or insufficient hot water. That said, the need for drainage during cold weather and the propane connection complexity make it less ideal for DIYers or those in colder climates. Its safety features, including automatic shutdown, add a layer of security, but the unit’s size and installation requirements could be a hurdle for some. Overall, it’s a good fit for users who prioritize precise temperature control and indoor installation.
Pros:- Precise digital temperature control for comfort and safety
- Quiet operation at 36dB
- High heating capacity supports multiple outlets
- Built-in freeze protection for moderate climates
Cons:- Requires drainage in cold weather, adding to installation complexity
- Propane connection may require professional setup
- Size may be less suitable for small or tight spaces
Best for: Families living in moderate climates who want a reliable, indoor propane heater with easy-to-read digital controls.
Not ideal for: Homeowners in extremely cold regions or those looking for a compact, minimalist design, due to its larger size and drainage needs.
- Heating Capacity:120,000 BTU
- Flow Rate:5.43 GPM
- Temperature Range:95°F-140°F
- Dimensions:20.55″H × 13.27″W × 5.91″D
- Noise Level:36dB
- Safety Features:Multiple-layer safety protection, automatic shutdown
Our verdict“This heater is best for users who want accurate temperature control and reliable indoor operation with propane fuel.”
How We Picked
To evaluate these tankless water heaters, I focused on performance metrics like flow rate and heating capacity, as well as usability factors such as size, installation complexity, and control features. Build quality and durability were also important, especially for outdoor models exposed to weather. I prioritized models offering reliable operation for typical household demands and considered their value based on features versus cost. The ranking reflects a balance of efficiency, ease of use, and suitability for different home sizes and needs, aiming to guide both budget-conscious buyers and those seeking premium options.Factors to Consider When Choosing Tankless Water Heaters
Choosing the right tankless water heater depends on several key factors that influence performance, installation, and long-term satisfaction. Understanding these can prevent common mistakes, like underestimating your household’s hot water needs or selecting a unit incompatible with your home’s energy sources. Here are the main considerations to keep in mind when selecting a tankless water heater:Flow Rate and Capacity
Flow rate determines how many fixtures can run simultaneously without a drop in water temperature. For larger households, a model with a higher GPM (gallons per minute) is essential to meet demand. Conversely, smaller homes or single fixtures can opt for lower-capacity units, saving space and cost. Always calculate your peak water usage to match the heater’s capacity, avoiding shortages or temperature fluctuations during busy times.
Fuel Type and Energy Efficiency
Gas models generally offer higher flow rates and lower operating costs over electric units, making them suitable for larger households. Electric heaters are more straightforward to install and often more compact, ideal for apartments or secondary locations. Considering the fuel source available and the energy efficiency ratings can help you choose a model that minimizes long-term expenses while fitting your home’s infrastructure.
Installation Considerations
Installation complexity varies; gas models require venting and proper clearance, which can increase upfront costs. Electric models usually need less space and simpler wiring, making them more DIY-friendly. Outdoor units expand placement options but demand weatherproofing, while indoor models need adequate space for connections. Planning for future maintenance and accessibility can prevent headaches down the line.
Size and Space Requirements
Space constraints are often overlooked but critical. Compact units are easier to install in tight spaces, but may sacrifice flow capacity. Larger, tankless units often require dedicated installation areas and proper ventilation. Consider your available space, future expansion plans, and local building codes to select a model that fits seamlessly into your home.
Cost and Long-Term Value
Initial purchase price is just one part of the total cost of ownership. High-efficiency models might cost more upfront but save money through lower energy bills. Balancing budget with expected performance and durability ensures you don’t overspend on features you won’t need. Remember to factor in installation costs and potential maintenance expenses when evaluating your options.
Frequently Asked Questions
Can I install a tankless water heater myself?
While some electric models are designed for DIY installation, most gas units and larger electric systems typically require professional installation due to venting, electrical wiring, and plumbing requirements. Improper installation can lead to safety hazards, reduced efficiency, or voided warranties. Evaluating your technical skills and local regulations can help determine whether a DIY approach is feasible or if hiring a licensed technician is best.
How do I know which size tankless water heater I need?
Determining the right size depends on your household’s hot water demand—specifically, how many fixtures you plan to run simultaneously. Calculate the GPM requirements for your typical usage, such as showers, sinks, and appliances. Choosing a unit with a slightly higher capacity than your peak demand provides a buffer for future needs and ensures consistent hot water without interruptions.
Are electric tankless heaters suitable for large households?
Electric models generally have lower flow rates compared to gas units, making them less ideal for large households with high simultaneous hot water demands. They work best for small homes, single fixtures, or supplemental heating. For larger families, gas or propane models tend to deliver the higher capacity needed to meet multiple demands at once while maintaining stable temperatures.
What maintenance does a tankless water heater require?
Tankless water heaters typically need periodic descaling or flushing, especially in areas with hard water, to prevent mineral buildup. Checking the filters and burners (for gas models) and inspecting for leaks or corrosion also extend the unit’s lifespan. Regular maintenance, often annually, ensures consistent performance and can help avoid costly repairs or early replacements.
Is it worth investing in a high-end model?
Premium tankless water heaters often boast higher efficiency, better build quality, and advanced features like smart controls or Wi-Fi connectivity. While they cost more initially, the savings on energy bills and reduced maintenance can make them a worthwhile investment over time. For those seeking reliability and long-term performance, opting for a higher-end model provides peace of mind and better value in the long run.
Conclusion
For the typical homeowner, the Rinnai RE160eP stands out as the best overall choice, offering a reliable flow rate and durable build. Budget-conscious buyers or small households might prefer the APUS Electric Heater for its affordability and space efficiency. Those with larger households or high demand should consider gas models like the Camplux Climatech 5 or Rinnai Propane Heater for their higher capacity. Beginners or those replacing an old unit should focus on models with straightforward installation and user-friendly controls. Carefully matching your household’s needs with these considerations will help you select the right tankless water heater in 2026.
