Choosing a tankless water heater means balancing capacity, energy efficiency, and budget. The Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater stands out as the best overall for its reliable performance and high flow rate, ideal for larger households. The Westinghouse 14kW Electric Tankless Water Heater is a top pick for those seeking WiFi connectivity and compact design, perfect for small apartments or point-of-use needs. However, the main tradeoffs in this category revolve around upfront costs versus long-term savings, flow rate versus energy consumption, and ease of installation versus capacity. Continue reading to see our detailed breakdown of these options, tailored to different needs and budgets.
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Key Takeaways
- High flow rate models like the Rheem RTG Series excel for larger households with multiple fixtures running simultaneously.
- Electric tankless heaters often cost less upfront but may require more power and have limited flow capacity for bigger households.
- Smart features like WiFi are more common in electric models, adding convenience but often at a premium price.
- Installation complexity varies; gas models usually require venting, while electric units are simpler to install but need adequate electrical wiring.
- Efficiency and capacity are key tradeoffs—picking a unit that matches your household’s hot water demand avoids underperformance or excessive energy use.
| tankless water heater | Power | Voltage | Flow Rate |
|---|---|---|---|
| 14kW Tankless Electric Water H | 14kW | 240V | — |
| Rheem RTG Series 7.0 GPM Natur | — | — | 7.0 GPM |
| 110V Electric Tankless Water H | 3000W | 110V | — |
| Rheem 11kW Tankless Electric W | 11kW | 240V | — |
| ThermoMate Tankless Water Heat | 11kW | 240V | 2.15 GPM |
| Rheem 18kW 240V Tankless Elect | 18kW | 240V | Up to 4.4 GPM |
| Westinghouse 14kW Tankless Ele | 14kW | 240V | 3.4 GPM |
| Rheem RTG Series 8.4 GPM Natur | — | — | 8.4 GPM |
| ORBEK 14kW Electric Tankless W | 14kW | 240V | — |
| Tankless Electric Water Heater | — | 110V | — |
| Rheem RTEX-24 24kW 240V Electr | 24kW, 240V single-phase | — | Up to 5.9 GPM |
More Details on Our Top Picks
14kW Tankless Electric Water Heater 240V for Sink & Shower, Gray
This 14kW electric unit excels in providing instant hot water for single or dual points, such as sinks and showers. Its compact size and smart temperature control make it ideal for limited spaces or dedicated points of use. Compared with larger models like the Rheem RTEX-24, this heater is not designed for whole-house capacity but offers superior efficiency and quick installation for small-scale needs. The main tradeoff is its limited flow rate and capacity—only suitable for 1-2 fixtures at once, and installation requires a robust 60-amp circuit. Still, for those needing a space-efficient, energy-saving solution for specific outlets, this pick delivers reliable performance.
Pros:- Energy-efficient with zero standby power consumption
- Instant hot water with high thermal efficiency
- Compact and easy to install in tight spaces
- Smart LED display for precise temperature control
Cons:- Requires a 60-amp circuit breaker, possibly complicating electrical setup
- Limited to 1-2 fixtures at a time, not suitable for whole-house use
Best for: Homeowners needing a dedicated point-of-use heater for a sink or shower in a small bathroom or kitchen.
Not ideal for: Large households or multi-bathroom homes where higher flow rates and capacity are required.
- Power:14kW
- Voltage:240V
- Dimensions:15.87″ x 11.14″ x 2.87″
- Water Connection:1/2″ NPT
- Temperature Range:86°F to 131°F
- Efficiency:99.8%
Our verdict“This model is best suited for small-scale point-of-use applications where space and energy efficiency are priorities.”
Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater Indoor
The Rheem RTG Series offers a powerful solution for large households, providing up to 7.0 GPM of continuous hot water and ample BTU output. It is better suited for whole-home installation compared to electric point-of-use units like the 14kW model, thanks to its higher flow rate and gas heating capacity. While it requires venting and an indoor space, its safety features—including leak detection and freeze protection—contribute to reliable operation. The main tradeoff is the higher initial cost and installation complexity, which may be a barrier for smaller homes or those seeking a quick upgrade. Nonetheless, this heater is ideal for those who need reliable, endless hot water across multiple fixtures.
Pros:- Provides endless hot water for multiple fixtures simultaneously
- Energy-efficient with significant utility savings
- Space-saving wall-mount design
- Advanced safety and leak protection features
Cons:- Requires indoor venting and proper installation
- Higher upfront cost and complexity compared to electric units
Best for: Large families or homes with multiple bathrooms seeking continuous hot water without capacity worries.
Not ideal for: Small apartments or homes with limited space and no venting options, due to installation requirements.
- Flow Rate:7.0 GPM
- BTU Output:160,000 BTUs
- Energy Factor:0.82 UEF
- Installation:Indoor, direct vent
- Safety Features:Freeze and flame failure protection
- Leak Protection:LeakGuard Leak Detection
Our verdict“This gas-powered heater is the best choice for large households that prioritize continuous hot water and can accommodate the installation requirements.”
110V Electric Tankless Water Heater, 3000W Instant Under Sink Water Heater with Digital Display
This 110V electric heater is designed for quick, on-demand hot water at a single fixture, making it ideal for kitchens or small bathrooms. Its compact size and LED digital display allow easy control and quick installation under sinks or small spaces. Compared with higher wattage models like the 14kW unit, it offers a lower flow rate—around 0.3 GPM—suitable for single faucets but not for showers or multiple fixtures simultaneously. Its safety features, including dry-boil and leakage protections, add peace of mind. However, the low flow rate and vertical installation restriction limit its use primarily to point-of-use applications where space and initial cost are priorities.
Pros:- Instant hot water with no preheating
- Compact, space-saving design
- Multiple safety protections including dry-boil and leak detection
- Easy to install with standard connections
Cons:- Not suitable for showers or high-demand fixtures
- Vertical mounting only limits placement options
- Flow rate too low for multiple outlets
Best for: Apartment dwellers or RV owners needing instant hot water at a single sink or small appliance.
Not ideal for: Homes requiring hot water for showers or multiple fixtures at once, due to limited flow capacity.
- Power:3000W
- Voltage:110V
- Temperature Rise:82°F (0.3 GPM)
- Material:Stainless steel and ABS
- Display:LED digital
- Max Temperature:131°F
Our verdict“This heater is best for small, single-fixture applications where space and quick installation are key priorities.”
Rheem 11kW Tankless Electric Water Heater – 240V, Multi-Fixture
The Rheem 11kW electric heater strikes a balance between capacity and compactness, providing up to 2.68 GPM—enough for several fixtures but not for simultaneous high-demand use. Its digital thermostatic controls allow precise temperature setting in 1-degree increments, which appeals to those who want fine control. Compared with the larger 14kW electric units, this model offers easier installation with a lower power draw, yet it still supports multiple outlets for moderate household needs. Its main drawback is the electrical capacity requirement—needing a 50-amp breaker and a 100-amp panel—making it less suitable for homes with limited electrical service. This makes it ideal for small to medium households with proper electrical infrastructure.
Pros:- On-demand hot water saves energy by eliminating standby heating
- Compact, space-efficient design
- No venting required simplifies installation
- Precise digital temperature control
Cons:- Requires a significant electrical capacity—50-amp breaker and 100-amp panel
- Limited flow rate may not support multiple heavy-use fixtures simultaneously
Best for: Small to medium households seeking reliable hot water for multiple fixtures without the complexity of gas venting.
Not ideal for: Homes with insufficient electrical capacity or large households with high simultaneous hot water demand.
- Power:11kW
- Voltage:240V
- Max Flow Rate:2.68 GPM
- Temperature Range:80°F – 140°F
- Breaker Requirement:50Amp double-pole
- Wiring:#8 AWG copper
Our verdict“This model suits small to mid-sized households with proper electrical wiring who need reliable, multi-fixture hot water without gas installation.”
ThermoMate Tankless Water Heater Electric 11kW 240V On Demand Instant Hot Water Heater for Point of Use
The ThermoMate 11kW heater combines reliable instant hot water with energy-saving self-modulation, making it suitable for point-of-use applications in tight spaces. Its durability is enhanced by a cast aluminum heating chamber, and safety protections like leak prevention and overheating safeguard operation. Compared with smaller 110V models, this 11kW unit offers higher flow rates—around 2.15 GPM at a 35°F rise—making it a better fit for multiple fixtures in a single location. However, it still requires a 50Amp double-pole breaker and cannot support high-demand scenarios like multiple showers. This heater is best for small households or commercial applications where space and efficiency matter most.
Pros:- Provides instant, continuous hot water
- Energy-efficient self-modulating technology
- Durable construction with leak-proof features
- Compact, space-saving design
Cons:- Requires a 50Amp double-pole breaker, increasing installation complexity
- Flow rate may be insufficient for multiple fixtures or high-demand use
- Maximum temperature limited to 131°F
Best for: Homeowners wanting a durable, energy-efficient point-of-use heater for kitchens or small bathrooms.
Not ideal for: Large households or those needing hot water for multiple fixtures simultaneously, due to flow and capacity limits.
- Power:11kW
- Voltage:240V
- Flow Rate:2.15 GPM
- Max Temperature:131°F
- Breaker Required:50Amp
- Connection:1/2” NPT
Our verdict“This heater works best for small-scale, point-of-use applications prioritizing durability and energy efficiency in limited spaces.”
Rheem 18kW 240V Tankless Electric Water Heater, Gray
The Rheem 18kW electric tankless heater stands out for its precise digital thermostatic control, which offers +/-1 degree accuracy, making it ideal for those who want reliable temperature management. Its self-modulating technology optimizes energy use, unlike less advanced models like the Westinghouse 14kW, which lack such efficiency features. The copper immersion heating elements are durable and field serviceable, simplifying maintenance. However, its 4.4 GPM flow rate can be limiting in colder climates with multiple simultaneous fixtures, and it may require electrical panel upgrades. This unit makes the most sense for homeowners with moderate hot water needs who prioritize control and efficiency without extensive installation complexity.Pros:- Digital thermostatic control with +/-1 degree accuracy
- Self-modulating power reduces energy consumption
- Field-serviceable copper heating elements
- Simple installation with threaded connections
Cons:- May require electrical panel upgrades in some homes
- Flow rate of 4.4 GPM could limit simultaneous fixtures in colder climates
Best for: Small to medium households seeking efficient hot water with precise temperature control
Not ideal for: Homes with high simultaneous hot water demand or older electrical systems needing upgrades
- Power:18kW
- Voltage:240V
- Flow Rate:Up to 4.4 GPM
- Heating Elements:Copper immersion, field serviceable
- Temperature Control:External digital thermostatic with LED display (+/-1 degree accuracy)
- Water Connections:Bottom 3/4 inch NPT
Our verdict“This model is well-suited for those who want reliable, controllable hot water without extensive installation hurdles, but it’s less ideal for larger households with higher demand.”
Westinghouse 14kW Tankless Electric Water Heater, 240V, WiFi, Gray
This Westinghouse model earns its spot for integrating smart WiFi control, allowing remote temperature adjustments and voice commands via Alexa or Google Home, making it ideal for tech-savvy users. Its compact design offers a significant space-saving advantage over larger units like the Rheem 18kW, but it requires a dedicated 60A breaker and complex wiring, which could challenge DIY installers. The 3.4 GPM flow rate is suitable for smaller points of use, but might struggle during simultaneous fixtures or in colder environments. Compared to the Rheem, it emphasizes convenience and connectivity, making it better suited for single or limited-use applications where space and smart features are priorities.Pros:- Smart WiFi control compatible with Alexa and Google Home
- Compact wall-mountable design saves space
- Provides instant hot water within seconds
- ETL certified with multiple safety features
Cons:- Requires dedicated 60A double-pole breaker and complex wiring
- Limited to residential applications with small hot water needs
Best for: Tech-savvy homeowners or small households wanting smart control and space efficiency
Not ideal for: Large households or homes with high hot water demand, due to limited flow rate and installation complexity
- Power:14kW
- Voltage:240V
- Flow Rate:3.4 GPM
- Maximum Temperature:140°F
- Dimensions:9.56″ W x 12.59″ H x 3.28″ D
- Mount Type:Wall
Our verdict“Ideal for users seeking modern connectivity and space-saving design, but unsuitable for high-demand or DIY installation environments.”
Rheem RTG Series 8.4 GPM Natural Gas Tankless Water Heater Outdoor | 180,000 BTUs High Efficiency On Demand
The Rheem RTG outdoor gas heater provides on-demand hot water for multiple fixtures simultaneously, thanks to its high flow rate of 8.4 GPM and substantial 180,000 BTUs. It’s a standout choice for large households needing continuous hot water without storage tanks, surpassing electric models in capacity. Its outdoor installation eliminates indoor space concerns, but it requires professional setup and may be vulnerable to weather if not installed properly. Compared with electric options, this unit offers higher flow rates suitable for whole-home use but involves higher upfront costs and more complex installation. It makes the most sense for those with significant hot water needs and outdoor space for installation.Pros:- Provides endless hot water for multiple fixtures simultaneously
- High efficiency reduces utility bills
- Outdoor installation saves indoor space
- Digital temperature control with safety features
Cons:- Professional installation required
- Outdoor setup can be affected by weather conditions
- Higher initial cost compared to tank heaters
Best for: Large families or homes with multiple bathrooms needing reliable, whole-house hot water
Not ideal for: Homes lacking outdoor space or those preferring electric solutions due to ease of installation
- Flow Rate:8.4 GPM
- BTUs:180,000
- Fuel Type:Natural Gas
- Installation Type:Outdoor
- Efficiency:0.82 UEF
- Warranty:15-year heat exchanger, 5-year parts
Our verdict“Best suited for large households needing reliable, high-capacity hot water in outdoor settings, though it involves more complex installation and higher upfront investment.”
ORBEK 14kW Electric Tankless Water Heater, 240V On-Demand, 3.38 GPM
The ORBEK 14kW heater excels in providing on-demand hot water for 2-3 fixtures, making it a solid choice for small bathrooms or kitchens. Its compact size, roughly half the volume of traditional tank heaters, makes it ideal for tight spaces. The precise temperature control within 1°F, combined with multiple safety protections, ensures reliable performance. Compared to larger electric models like the Westinghouse 14kW, it offers similar flow but with a smaller footprint, ideal for point-of-use needs. However, its limited flow rate restricts use to a few fixtures simultaneously, and it requires a 60A dedicated circuit, making installation more demanding for some homeowners.Pros:- Endless hot water within its flow limits
- Compact, space-saving design
- Precise temperature control with LED display
- Multiple safety protections
Cons:- Flow rate limits to 3.38 GPM, restricting simultaneous use
- Requires dedicated 60A circuit and professional wiring
Best for: Small households or point-of-use applications needing precise temperature control in limited space
Not ideal for: Homes with multiple simultaneous hot water fixtures or higher flow requirements
- Power:14kW
- Voltage:240V
- Max Flow Rate:3.38 GPM
- Temperature Range:86°F – 140°F
- Dimensions:14.2″H x 9.5″L x 3.1″W
- Certification:ETL
Our verdict“Perfect for small-scale or point-of-use applications demanding reliable, precise hot water, but limited in capacity for larger households.”
Tankless Electric Water Heater 3000W, 110V with Digital Display
This ultra-compact electric heater provides instant hot water for small sinks, RVs, or camping setups, with a simple 3000W output. Its small form factor makes installation straightforward and suitable for temporary or limited use. The high thermal efficiency of 98% and integrated safety protections offer reliability in confined spaces. Unlike larger electric units, it cannot support showering or multiple fixtures simultaneously, but it excels as a point-of-use solution where space is at a premium. Its requirement for professional wiring and a 32A circuit limits easy DIY installation for some users.Pros:- Compact and lightweight design
- High thermal efficiency of 98%
- Multiple safety protections including waterproofing
- Easy to install with standard connections
Cons:- Not suitable for showers or multiple fixtures
- Limited to vertical installation only
Best for: RVs, camping, or small kitchens needing instant hot water at a single point
Not ideal for: Whole-house hot water needs or shower applications due to flow and temperature limitations
- Power Source:AC
- Voltage:110V
- Heat Output:3000W
- Maximum Temperature:131°F
- Protection Features:Leakage, over-temperature, waterproof
- Dimensions:4.32″W x 7.86″H
Our verdict“Ideal for portable or small-scale hot water needs where space and instant delivery are paramount, but unsuitable for whole-house or multi-point use.”
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
The Rheem RTEX-24 makes a compelling case for households that demand multiple fixtures to run simultaneously, thanks to its impressive flow rate of up to 5.9 GPM. Unlike smaller electric models, such as the 110V Electric Tankless Water Heater, which are better suited for single fixtures, this unit can handle larger demand without sacrificing temperature stability. Its digital thermostatic controls allow precise adjustments in 1-degree increments, ensuring consistent comfort, while its compact design saves significant space—being 90% smaller than traditional tank heaters. However, the high electrical requirements—needing three 40-amp double-pole breakers and a minimum 200-amp service panel—pose installation challenges, especially for older homes. Professional installation is strongly recommended, and proper sizing is essential to avoid underperformance. This model is best suited to those upgrading their electrical system or with a dedicated circuit, but it’s not ideal for homes with limited electrical capacity or minimal hot water needs.
Pros:- Delivers up to 5.9 GPM, suitable for multiple fixtures simultaneously
- Space-saving design, 90% smaller than traditional tank heaters
- Energy-efficient, heats water only when needed
- Precise digital temperature control for consistent outputs
Cons:- Requires significant electrical capacity and professional installation
- High upfront wiring and electrical panel upgrade costs
Best for: Homeowners with high hot water demand who are prepared for a dedicated electrical upgrade
Not ideal for: Small households or apartments with limited electrical service, due to its high wiring requirements
- Power:24kW, 240V single-phase
- Flow Rate:Up to 5.9 GPM
- Temperature Range:80°F – 140°F (26°C – 60°C)
- Wiring Requirements:Three 40-amp double-pole breakers, #8 AWG copper conductors
- Recommended Service Panel:Minimum 200-amp household electrical service
- Warranty:5-Year Leak, 1-Year Parts
Our verdict“This unit is ideal for larger homes with high hot water needs and the electrical capacity to support it, but less suitable for small or retrofit installations.”
How We Picked
These products were selected based on their performance, build quality, versatility, and value for different household sizes and budgets. I prioritized models with reliable flow rates, energy efficiency, and user-friendly features. Products were ranked considering ease of installation, maintenance needs, and overall durability. To ensure broad applicability, I included options suitable for both small apartments and large homes, balancing premium features with affordability. This approach ensures a well-rounded lineup that addresses common buyer priorities and tradeoffs in the tankless water heater category.Factors to Consider When Choosing Tankless Water Heater
When choosing a tankless water heater, understanding key factors can help you select the best fit for your household. From capacity to energy consumption, each factor impacts performance and long-term satisfaction. Making an informed choice involves evaluating your hot water needs, available space, and budget to avoid common pitfalls like undersizing or overspending.Flow Rate and Capacity
Flow rate determines how much hot water the unit can produce simultaneously. Larger households with multiple fixtures need higher GPM (gallons per minute) ratings to prevent running out of hot water. Oversizing results in unnecessary energy costs, while undersizing causes inadequate hot water. Carefully estimate your household’s peak demand and choose a unit that matches or slightly exceeds it for optimal performance.
Energy Source and Efficiency
Electric models tend to be easier to install and maintain but might consume more electricity, affecting operating costs. Gas units offer higher capacity and efficiency for bigger households but require venting and proper installation. Consider your home’s existing infrastructure and long-term energy costs. Investing in a high-efficiency unit can save money over time, especially in larger households or colder climates.
Installation and Space Requirements
Some models are compact and suitable for small spaces or point-of-use installations, while others require more room and proper venting. Gas units often need venting and clearance, adding to installation complexity and cost. Electric units are generally simpler to install but need a dedicated high-capacity electrical circuit. Factor in your available space and whether professional installation is feasible within your budget.
Cost and Long-Term Savings
Initial purchase and installation costs vary widely. Cheaper electric units might seem attractive but could lead to higher energy bills if undersized. Conversely, investing in a premium gas model can offer greater reliability and lower operating costs over time. Balance your upfront budget with potential savings on energy and maintenance when selecting a unit.
Smart Features and User Interface
Many electric models now include WiFi connectivity and digital displays, offering convenience and remote control. These features can enhance user experience but typically add to the cost. If tech integration matters to you, prioritize models with these capabilities, but be aware that simpler units often deliver the essentials at a lower price point.
Frequently Asked Questions
Can I install a tankless water heater myself?
While some electric models are designed for easy installation, most tankless water heaters, especially gas units, require professional installation due to venting, electrical, and plumbing considerations. Proper installation ensures safety, efficiency, and compliance with local codes. Attempting a DIY approach without proper expertise can lead to costly mistakes and potential hazards, so consulting a licensed technician is generally recommended.
How big of a tankless water heater do I need for my household?
The size you need depends on your household’s hot water demand. For example, a small apartment with one bathroom might do well with a unit rated around 3-4 GPM, while a larger family with multiple bathrooms may require 8 GPM or more. Estimating your peak simultaneous usage helps avoid underperformance and ensures everyone has enough hot water when needed.
Are electric tankless water heaters more energy-efficient than gas ones?
Electric models often have higher efficiency ratings because they convert nearly all electrical energy into heat. However, they may require significant electrical capacity and can be less cost-effective in large households. Gas units, while slightly less efficient physically, may be more economical for high-demand scenarios due to their higher flow rates and lower operating costs in certain regions.
What maintenance is required for a tankless water heater?
Maintenance typically involves flushing the unit annually to prevent mineral buildup, especially in hard water areas. Gas units may require vent inspection and combustion checks, while electric models generally need less upkeep. Regular maintenance extends the lifespan of the unit and maintains performance, making it a worthwhile investment over time.
How long does a tankless water heater last?
Most tankless water heaters have a lifespan of around 20 years with proper maintenance. Factors like water quality, usage patterns, and installation quality influence longevity. Investing in a high-quality model and performing routine upkeep can maximize your unit’s service life and ensure reliable hot water for years to come.
Conclusion
For households seeking the best overall performance, the Rheem RTG Series offers high capacity and reliability. Budget-conscious buyers will appreciate the value of electric models like the Westinghouse 14kW, which combine affordability with smart features. Those looking for a premium experience should consider units with advanced controls and high efficiency, like the Rheem RTEX-24. First-time buyers or small apartments benefit from simpler, compact options, while large families need high-flow, gas-powered systems. Defining your specific needs and budget helps narrow down the ideal choice for your home.
