A tankless water heater provides hot water on demand, offering energy savings and space efficiency compared to traditional tanks. The Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater stands out as the overall best for its reliability and high flow rate. For electric options, the Rheem 24kW Tankless Electric Water Heater delivers strong performance for larger households, while the ThermoMate Electric Water Heater offers a compact, budget-friendly choice for small spaces. Buyers face tradeoffs between fuel type, flow rate, installation complexity, and upfront cost. Continue reading for a detailed breakdown of each model’s strengths and weaknesses.
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Key Takeaways
- Flow rate is a key factor: higher GPM models better serve larger households with multiple outlets running simultaneously.
- Electric models tend to be more compact and easier to install, but often have lower flow rates and higher energy costs for bigger households.
- Gas-powered units generally offer higher capacity and better performance for larger homes, but require venting and more complex installation.
- Budget options can be effective for small households or point-of-use needs, but may lack durability or advanced features of premium models.
- Choosing the right size and fuel type depends heavily on your household size, hot water demand, and existing infrastructure.
| tankless water heater | Flow Rate | Power | Voltage |
|---|---|---|---|
| Rheem RTG Series 7.0 GPM Natur | 7.0 GPM | — | — |
| ThermoMate Tankless Electric W | 2.15 GPM at 35°F rise | 11kW | 240V |
| 14kW Tankless Electric Water H | 3.3 GPM | 14 KW | 240V |
| 14kW Tankless Electric Water H | 3.38 GPM | 14 KW | 240V |
| Rheem RTG Series 8.4 GPM Natur | 8.4 GPM | — | — |
| Rheem 240V Tankless Water Heat | up to 3.17 GPM | 13kW | 240V |
| Tankless Electric Water Heater | 0.3GPM to 0.5GPM | 3000W | 110V |
| Rheem 11kW Multi Fixture Tankl | up to 2.68 GPM | 11kW | 240V |
| Rheem 18kW 240V Tankless Elect | up to 4.4 GPM | 18kW | 240V |
| Rheem RTEX-24 24kW 240V Electr | up to 5.9 GPM | 24kW | 240V |
| 110V Tankless Electric Water H | 0.3GPM to 0.5GPM | 3000W | 110V |
More Details on Our Top Picks
Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater Indoor
This model stands out for its ability to supply continuous hot water for large households, matching the capacity of outdoor units like the Rheem RTG Series 8.4 GPM but in an indoor, space-saving design. Its high efficiency, with an energy factor of 0.82 UEF, helps reduce ongoing costs, making it ideal for energy-conscious buyers. The safety features and leak detection add peace of mind, though proper venting requirements can complicate installation and increase upfront costs. Compared to electric options, this natural gas heater offers greater flow rate and suitability for multi-bathroom homes, but at a higher initial investment.
Pros:- Provides endless hot water for multiple fixtures simultaneously
- High energy efficiency reduces operational costs
- Compact wall-mount design saves space
- Includes advanced safety and leak detection features
Cons:- Requires proper venting for indoor installation, adding complexity
- Higher upfront cost compared to traditional tank heaters
Best for: Large families or multi-bathroom homes seeking reliable, high-capacity hot water with energy savings
Not ideal for: Small apartments or single-bathroom households where installation complexity and cost outweigh benefits
- 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 wanting reliable, energy-efficient hot water with minimal space footprint.”
ThermoMate Tankless Electric Water Heater, 11kW, 240V, On Demand Instant Hot Water, 2.15 GPM at 35°F Rise
This pick makes the most sense for single-point applications or small households, especially where only a couple of fixtures need hot water at once. Its self-modulating technology offers significant energy savings—up to 60%—compared to less efficient electric models like the 14kW unit, but the maximum flow rate of 2.15 GPM limits its capacity for larger households. Its compact, wall-mounted design fits into tight spaces easily, and durable materials ensure longevity, though the need for a dedicated 50A breaker can complicate installation for some users. Unlike larger electric units, this model prioritizes efficiency over high flow, making it ideal for low-demand scenarios.
Pros:- Provides instant, continuous hot water for small-scale needs
- Self-modulating technology cuts energy costs significantly
- Compact, space-efficient design
- Durable cast aluminum chamber resists corrosion
Cons:- Limited flow rate unsuitable for high-demand households
- Installation requires a dedicated 50A breaker
Best for: Small households or point-of-use setups needing reliable hot water with energy savings
Not ideal for: Large families or homes requiring simultaneous multiple fixtures beyond 2-3 points
- Power:11kW
- Voltage:240V
- Flow Rate:2.15 GPM at 35°F rise
- Max Temperature:131°F
- Certifications:ETL
Our verdict“This electric heater is best for small-scale applications where energy efficiency and space-saving are priorities.”
14kW Tankless Electric Water Heater 240V for Sink & Shower, Gray
This model is designed for small households or single fixtures, with a flow rate of 3.3 GPM making it suitable for simultaneous sink and shower use, unlike higher-capacity electric units like the 14kW model that might struggle with multiple high-demand fixtures. Its smart temperature control and safety features, such as leak and overheat protections, enhance reliability, though installation requires a 60A circuit breaker and professional setup. Compared to the 11kW model, this heater offers higher flow capacity, but it still isn’t meant for large households. It balances energy efficiency with ease of installation in limited spaces, making it ideal for targeted applications.
Pros:- Delivers instant hot water with high thermal efficiency
- Precise LED temperature control
- Space-saving wall-mounted design
- Built-in safety protections
Cons:- Requires a 60A circuit breaker, complicating installation
- Limited to 1-2 points of use
Best for: Small households or specific points of use needing reliable hot water with straightforward installation
Not ideal for: Homes with multiple simultaneous fixtures or higher flow demands
- Power:14 KW
- Voltage:240V
- Flow Rate:3.3 GPM
- Maximum Temperature:131°F
- Certifications:ETL
Our verdict“This electric heater is ideal for small, targeted hot water needs where space and efficiency matter most.”
14kW Tankless Electric Water Heater, On Demand, 240V, 3.38 GPM
Compared with the 11kW model, this 14kW heater offers a higher flow rate of 3.38 GPM, making it more suitable for small to medium households with 2-3 fixtures running simultaneously. Its space-saving design, combined with advanced safety features, makes it easy to install and reliable for everyday use. The precise temperature control and LED display enhance user convenience, but like other electric options, it still demands professional wiring and a dedicated 60A breaker. This model balances capacity and efficiency, but may fall short in larger homes where higher flow rates or multiple simultaneous outlets are needed.
Pros:- Provides instant hot water with high efficiency
- Compact, space-efficient design
- Advanced safety features like leakage and over-temperature protection
- Precise temperature control
Cons:- Requires a dedicated 60A breaker and professional wiring
- Flow rate may be insufficient for large households
Best for: Small to medium households seeking reliable, efficient hot water for multiple fixtures
Not ideal for: Large households with high simultaneous demand or multiple bathrooms
- Power:14 KW
- Voltage:240V
- Flow Rate:3.38 GPM
- Maximum Temperature:140°F
- Dimensions:9.5″W x 14.2″H x 3.1″D
Our verdict“This heater offers a good balance of capacity and safety for small to medium households with moderate hot water needs.”
Rheem RTG Series 8.4 GPM Natural Gas Tankless Water Heater Outdoor
This outdoor model offers a higher flow rate than the indoor version, with 8.4 GPM, making it well-suited for large households or homes with multiple bathrooms. Its durability and outdoor design eliminate the need for venting, simplifying installation in suitable climates. Compared to the 7.0 GPM indoor heater, it provides more capacity for simultaneous fixtures, but outdoor installation requires ample space and a proper mounting area. Its high efficiency (0.82 UEF) supports ongoing savings, though the higher initial cost and outdoor-only placement limit flexibility compared to indoor models.
Pros:- High flow rate supports multiple fixtures simultaneously
- Durable outdoor design withstands weather
- Energy-efficient with significant cost savings
- Long warranty on the heat exchanger
Cons:- Requires professional outdoor installation and mounting
- Higher upfront cost compared to smaller or indoor units
- Dependent on outdoor space availability
Best for: Large households or multi-bathroom homes requiring outdoor installation with high flow capacity
Not ideal for: Small homes or indoor spaces where outdoor placement isn’t possible
- Flow Rate:8.4 GPM
- BTU:180,000
- Efficiency:0.82 UEF
- Installation:Outdoor
- Warranty:15-year heat exchanger, 5-year parts
Our verdict“This outdoor unit is ideal for large households wanting high capacity without indoor venting constraints.”
Rheem 240V Tankless Water Heater RTEX-13, Gray
The Rheem RTEX-13 stands out for its high energy efficiency, reaching 99.8%, and its precise digital temperature control, making it ideal for small households or apartments. Compared with larger models like the Rheem RTEX-24, it offers a lower flow rate of 3.17 GPM, which may limit use during multiple simultaneous fixtures. Its durable copper heating elements and easy installation features make it a practical choice for DIY enthusiasts. The main tradeoff is its limited flow rate, making it less suitable for bigger households with high hot water demand. This model is best for individuals or couples who need reliable, on-demand hot water without the need for multiple outlets at once.
Pros:- High 99.8% energy efficiency for lower utility bills
- Digital display allows precise temperature adjustments
- Easy to install with included adapters
- Durable copper heating elements ensure longevity
Cons:- Flow rate may be insufficient for multiple fixtures at once
- Requires 240V power supply, which may need electrical upgrades
Best for: Small households or apartments needing dependable hot water with minimal space and energy use
Not ideal for: Large families or homes with multiple fixtures running simultaneously, due to its limited flow rate
- Model:RTEX-13
- Voltage:240V
- Flow Rate:up to 3.17 GPM
- Power:13kW
- Energy Efficiency:99.8%
- Water Connection:1/2 inch NPT and compression fittings
- Temperature Control:Digital, +/- 1°F accuracy
Our verdict“This is a solid pick for small households prioritizing efficiency and precise control.”
Tankless Electric Water Heater, 3000W, 110V, Digital Display, Compact & Wall-Mounted
This compact electric tankless water heater excels in small spaces such as kitchens, RVs, or camping setups, offering instant hot water with a straightforward wall-mount design. Unlike the Rheem 11kW multi-fixture model, it’s designed for very limited flow rates of 0.3 to 0.5 GPM, making it unsuitable for showers or multiple fixtures. Its safety features, including leakage and over-temperature protections, add reliability for portable or temporary use. The main drawback is its limited flow capacity, so it’s best for single fixtures or small sinks. This unit is ideal for users needing occasional hot water in tight spots, like RV owners or small apartment occupants.
Pros:- Ultra-compact and space-saving design
- Fast instant hot water with digital temperature control
- Multiple safety protections ensure reliable operation
- Easy to install with standard connections
Cons:- Limited flow rate unsuitable for showers
- Requires specific electrical wiring and breakers
- Not designed for high-flow applications
Best for: RVers, tiny homes, or small sinks where space and safety are priorities
Not ideal for: Homes with multiple fixtures or high hot water demand, since it can’t handle simultaneous flow
- Power:3000W
- Voltage:110V
- Flow Rate:0.3GPM to 0.5GPM
- Temperature Rise:82°F to 131°F
- Waterproof Rating:IPX4
- Installation:Vertical only
Our verdict“This is a perfect choice for small, space-constrained environments where occasional hot water suffices.”
Rheem 11kW Multi Fixture Tankless Electric Water Heater – 240V
The Rheem 11kW electric tankless heater strikes a balance between size and capacity, offering up to 2.68 GPM, perfect for small to medium households. It compares favorably to the Rheem 18kW model, which provides higher flow but requires a more robust electrical setup. This model’s space-saving design and energy efficiency make it suitable for homes with limited space but multiple fixtures needing hot water. The main limitation is its flow rate—if your household frequently runs multiple fixtures simultaneously, it could fall short. It’s an excellent option for homes that need reliable hot water without installing larger, more complex units.
Pros:- Reliable hot water for multiple fixtures
- Compact and space-efficient design
- Energy-efficient operation
- Includes a 5-year leak and 1-year parts warranty
Cons:- Limited flow rate of 2.68 GPM
- Requires professional electrical installation
- May need electrical upgrades in older homes
Best for: Small to medium households with moderate hot water demand and limited electrical capacity
Not ideal for: Large households or homes with high simultaneous hot water needs, due to its limited flow rate
- Power:11kW
- Voltage:240V
- Flow Rate:up to 2.68 GPM
- Temperature Range:80°F – 140°F
- Warranty:5-year leak, 1-year parts
- Water Connection:3/4 inch NPT
Our verdict“This model is suited for small to medium households seeking reliable, space-efficient on-demand hot water.”
Rheem 18kW 240V Tankless Electric Water Heater, Gray
The Rheem 18kW tankless electric heater offers a significant flow capacity of up to 4.4 GPM, making it suitable for larger households or multiple simultaneous fixtures. Compared to the 11kW model, it provides higher hot water output but demands a more robust electrical system, including potentially upgrading your circuit breakers. Its digital thermostat and self-modulation optimize energy use, adjusting power based on demand. The primary tradeoff is its higher energy consumption and the need for a 240V supply capable of handling 18kW. If your household demands high flow, this model reduces the risk of running out of hot water during peak times.
Pros:- High flow rate of 4.4 GPM for multiple fixtures
- Self-modulation for energy efficiency
- Digital thermostat with LED display
- Durable copper heating elements
Cons:- Requires substantial electrical upgrades
- Higher energy consumption
- Potential overkill for small households
Best for: Larger families or homes with multiple fixtures running at once
Not ideal for: Small apartments or single fixture setups, due to its higher power requirements and flow capacity
- Power:18kW
- Voltage:240V
- Flow Rate:up to 4.4 GPM
- Temperature Range:80°F – 140°F
- Connection Size:3/4 inch NPT
- Color:Gray
Our verdict“This unit is best for larger homes needing robust flow capacity and reliable on-demand hot water.”
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater
The Rheem RTEX-24 provides up to 5.9 GPM, making it the most capable among this lineup for high-flow needs. Its digital temperature controls and energy-efficient operation align with those of the Rheem 18kW model, but with a higher power rating suitable for larger households or simultaneous fixtures. Unlike smaller models, this unit can handle more extensive hot water demands, though its installation complexity increases with the need for a dedicated electrical setup. The main downside is that it still requires professional wiring and a large electrical panel capacity, which might be a barrier for some homes. It’s the best choice when multiple fixtures need hot water at once without sacrificing flow rate.
Pros:- High flow rate of 5.9 GPM for multiple fixtures
- Digital controls for precise temperature management
- Energy-efficient, heats water on demand
- Long 5-year leak warranty
Cons:- Requires significant electrical capacity
- More complex installation process
- Higher upfront cost
Best for: Large households or homes with multiple fixtures running simultaneously
Not ideal for: Small homes or apartments with limited electrical capacity, due to high power needs
- Power:24kW
- Voltage:240V
- Flow Rate:up to 5.9 GPM
- Temperature Range:80°F – 140°F
- Warranty:5-year leak, 1-year parts
Our verdict“This model is ideal for large households that need high flow and reliable hot water without compromise.”
110V Tankless Electric Water Heater, 3000W, Instant Hot Water with Digital Display for Kitchen and Bathroom
This 110V tankless electric water heater stands out for its compact size and straightforward design, making it ideal for small spaces like kitchens or RVs. Unlike higher-capacity models such as the ThermoMate 11kW heater, it offers a modest flow rate—only 0.3 to 0.5 GPM—which limits its use to sinks or small appliances rather than showers. Its digital display and safety features like leakage and overheating protections enhance reliability, but its vertical-only installation restricts placement options. Compared with larger electric units, this model excels in ease of installation and efficiency for low-demand applications, though it can’t handle simultaneous high-flow needs. This pick makes the most sense for users who need quick, space-efficient hot water for single fixtures, not for whole-house or high-demand setups.
Pros:- Highly space-efficient with wall-mounted design
- Provides instant hot water with high thermal efficiency
- Includes multiple safety protections for peace of mind
- Easy to install with pre-drilled holes and standard connections
Cons:- Limited flow rate restricts use to sinks or small appliances
- Vertical installation only, no horizontal mounting option
- Not suitable for shower or high-demand applications
Best for: Small households or RV owners needing instant hot water at a single point of use
Not ideal for: Families requiring multiple outlets or shower use, due to its limited flow rate and vertical installation only
- Power:3000W
- Voltage:110V
- Water Temperature Rise:82°F to 131°F
- Flow Rate:0.3GPM to 0.5GPM
- Protection Features:IPX4 waterproof, leakage, dry boil, overheating
- Material:Stainless steel and ABS
- Installation:Wall-mounted, vertical only
- Certifications:ETL
Our verdict“This model is best suited for users needing a compact, reliable hot water source for low-flow applications like kitchen sinks or RVs.”
How We Picked
To evaluate these tankless water heaters, I focused on performance, reliability, ease of installation, and value for money. Models were compared based on flow rate, energy efficiency, build quality, and suitability for different household sizes and installation environments. Priority was given to products with proven durability and positive user feedback, ensuring they meet real-world demands. The ranking reflects a balance between capacity, ease of use, and cost, helping buyers select options aligned with their specific needs and budgets.Factors to Consider When Choosing Tankless Water Heater
When choosing a tankless water heater, understanding key factors can prevent costly mistakes and ensure your system meets your needs. Consider your household size, hot water demand, and existing fuel sources to select a suitable model. Beyond initial cost, long-term energy savings and installation complexity also matter. Here are some essential factors to keep in mind:Flow Rate and Capacity
Flow rate, measured in GPM (gallons per minute), determines how many fixtures can run simultaneously without a drop in water temperature. Larger households or homes with multiple bathrooms should prioritize higher GPM models. Conversely, smaller households or point-of-use setups might find lower-capacity units adequate. Matching your peak demand with a suitable flow rate prevents cold surprises during busy mornings or heavy use.
Fuel Type and Energy Efficiency
Gas models typically offer higher flow rates and are more cost-effective for large households, but require venting and more complex installation. Electric units are easier to install and better suited for smaller spaces or supplemental use, though they may lead to higher electricity bills. Additionally, look for ENERGY STAR-rated models that can reduce ongoing energy costs and improve environmental impact.
Installation Requirements
Installation complexity varies: gas units may need venting and professional setup, while electric models often install directly into existing wiring and plumbing. Consider your home’s existing infrastructure and whether upgrades are needed. Proper installation ensures safety, efficiency, and longevity, so investing in professional help can be worthwhile for complex setups.
Size and Space Considerations
Compact models are ideal for small spaces or point-of-use applications, but may sacrifice capacity. Larger units require more space and may involve more complex installation. Evaluate your available space carefully—measurements and clearances matter—and choose a model that fits comfortably while meeting your hot water needs.
Cost and Long-Term Value
Initial purchase price varies widely, with electric units generally being cheaper upfront. However, consider ongoing operation costs—electricity versus gas—and maintenance requirements. Investing in a higher-quality model can pay off through durability and energy savings, especially if your household demands high hot water volume regularly.
Frequently Asked Questions
Can a tankless water heater supply enough hot water for a large family?
Yes, but only if you select a model with a sufficiently high flow rate, typically above 7 GPM. Larger households often require multiple fixtures running simultaneously, so pairing a high-capacity unit with proper sizing is essential. Keep in mind that gas models generally deliver higher flow rates than electric ones, making them more suitable for extensive household needs.
Are electric tankless water heaters suitable for whole-house use?
Electric tankless water heaters can work for small households or specific applications like a single bathroom or kitchen, but they often lack the capacity needed for larger homes. They also tend to have higher operating costs if used extensively. For whole-house use in larger households, gas models or higher-capacity electric units are usually more practical and cost-effective.
What are the main installation considerations for gas vs. electric models?
Gas units require venting, proper gas line connections, and usually professional installation, which can add to costs. Electric models are generally simpler to install, often fitting into existing electrical outlets, but may require upgrading your wiring or circuit capacity. Assess your home’s infrastructure and budget for installation to avoid surprises later.
Do tankless water heaters need regular maintenance?
While generally low-maintenance, tankless water heaters benefit from periodic flushing to prevent mineral buildup, especially in areas with hard water. Gas units might also need vent inspection and burner cleaning. Proper maintenance prolongs their lifespan and maintains efficiency, making regular checkups a wise investment.
Is it better to buy a larger or smaller capacity tankless heater?
Choosing the right size depends on your household size and hot water demand. Larger capacity units provide more hot water simultaneously but cost more upfront and may be overkill for small homes. Smaller units are more economical for minimal needs but can struggle during peak use. Accurate sizing ensures comfort without unnecessary expense.
Conclusion
The best overall choice for most households remains the Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater, thanks to its reliable performance and capacity. Budget-conscious buyers or small households should consider electric models like the ThermoMate Electric Water Heater for simplicity and affordability. For those seeking premium performance, the Rheem 24kW Electric Tankless Water Heater offers excellent capacity, though at a higher price point. Beginners or small spaces benefit from compact, point-of-use models, while larger families or homes with multiple bathrooms should prioritize high-flow gas units. Matching your household needs with these options ensures you get hot water reliably and efficiently in 2026.
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