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10 Best Tankless Hot Water Heaters 2025 in the United States
#1
Winner
NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater, Indoor or Outdoor Water Heater, Up to 11.1 GPM, 199,000 BTU
The Rinnai RX199iN is a powerful tankless water heater that stands out for its impressive flow rate of up to 11.1 gallons per minute, making it suitable for homes with multiple fixtures needing hot water simultaneously. It's designed to operate on either natural gas or propane, giving you flexibility depending on your fuel source. The energy efficiency is top-notch, boasting a UEF rating of .98, which means it uses energy very effectively, potentially saving you on utility bills.
Rating
10.0
Chosen by1,327
Flow Rate (GPM)
Fuel Type
Size and Installation
Most important from
262 reviews
#2
Rheem 18kW 240V Tankless Electric Water Heater, Gray
The Rheem 18kW 240V Tankless Electric Water Heater in Gray offers several appealing features for those in need of a compact and efficient water heating solution. The primary advantages of this model include its advanced self-modulation technology, which helps adjust power based on the hot water demand, ensuring energy efficiency and cost savings. Additionally, it boasts a flow rate of up to 4.4 GPM, which is suitable for small to medium households, providing enough hot water for multiple uses simultaneously.
Rating
8.5
Temperature Rise
Size and Installation
Most important from
2040 reviews
#3
Rinnai RL75IN Tankless Hot Water Heater, 7.5 GPM, Natural Gas, Indoor Installation
The Rinnai RL75IN Tankless Hot Water Heater offers a robust performance with a flow rate of 7.5 gallons per minute (GPM), making it capable of supplying hot water to up to 5 fixtures simultaneously. This is particularly advantageous for families or homes with multiple bathrooms. The unit uses natural gas, which can be more cost-effective compared to electric models, and it is designed for indoor installation, saving outdoor space and making it suitable for various home layouts.
Rating
7.6
Flow Rate (GPM)
Energy Efficiency
Size and Installation
Most important from
1047 reviews
Top 10 Best Tankless Hot Water Heaters 2025 in the United States
#1
Winner
NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater, Indoor or Outdoor Water Heater, Up to 11.1 GPM, 199,000 BTU
NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater, Indoor or Outdoor Water Heater, Up to 11.1 GPM, 199,000 BTU
Flow Rate (GPM): 11.1
Energy Efficiency: UEF .98
Fuel Type: Natural gas or propane
Size and Installation: 18.5"W x 30.11"H, Wall mount
Chosen by 1327 this week
Rheem 18kW 240V Tankless Electric Water Heater, Gray
Rheem 18kW 240V Tankless Electric Water Heater, Gray
Flow Rate (GPM): 4.4
Energy Efficiency: self-modulation technology
Fuel Type: Electric
Size and Installation: 14.5"W x 18.25"H, 3/4 inch NPT
Rinnai RL75IN Tankless Hot Water Heater, 7.5 GPM, Natural Gas, Indoor Installation
Rinnai RL75IN Tankless Hot Water Heater, 7.5 GPM, Natural Gas, Indoor Installation
Flow Rate (GPM): 7.5
Fuel Type: Natural Gas
Size and Installation: 17.5"W x 31"H, Indoor
Warranty and Support: Up to 12 years heat exchanger
Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water Heater, 8.4 GPM
Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water Heater, 8.4 GPM
Flow Rate (GPM): 8.4
Energy Efficiency: GAMA certified
Fuel Type: Natural Gas
Size and Installation: 13.5"W x 20.75"H, 39.2 lbs, Wall, Outdoor
Rinnai RE140iN Non-Condensing Natural Gas Tankless Water Heater, Up to 5.3 GPM, Indoor Installation, 140,000 BTU
Rinnai RE140iN Non-Condensing Natural Gas Tankless Water Heater, Up to 5.3 GPM, Indoor Installation, 140,000 BTU
Flow Rate (GPM): 5.3
Energy Efficiency: High
Fuel Type: Natural Gas
Size and Installation: 14.05"W x 27.28"H, Wall-mount
Warranty and Support: Up to 15 years
Related Products
Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Tankless Water Heater, 199,000 BTU, 11.1 GPM
Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Tankless Water Heater, 199,000 BTU, 11.1 GPM
Flow Rate (GPM): 11.1 gallons per minute
Energy Efficiency: 96%
Fuel Type: natural gas or propane
Temperature Rise: 185°F
Size and Installation: 18.5" x 30", wall mount, vented
Rheem RTG-84DVLP-3 High Efficiency Non-Condensing Indoor Tankless Liquid Propane Water Heater, 8.4 GPM
Rheem RTG-84DVLP-3 High Efficiency Non-Condensing Indoor Tankless Liquid Propane Water Heater, 8.4 GPM
Flow Rate (GPM): 8.4
Energy Efficiency: High Efficiency
Fuel Type: Liquid Propane
Size and Installation: 13.5"W x 24.2"H x 10.27"D
Rheem RTG-84DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Heater, 8.4 GPM
Rheem RTG-84DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Heater, 8.4 GPM
Flow Rate (GPM): 8.4 gallons per minute
Energy Efficiency: 0.82
Fuel Type: natural gas
Temperature Rise: 140 degrees Fahrenheit
Size and Installation: 13.5"W x 24.2"H, wall-mountable
Rinnai V75IN Tankless Hot Water Heater, 7.5 GPM, Natural Gas, Indoor Installation
Rinnai V75IN Tankless Hot Water Heater, 7.5 GPM, Natural Gas, Indoor Installation
Flow Rate (GPM): 7.5 Gallons Per Minute
Energy Efficiency: Energy Factor 0.82
Fuel Type: Natural Gas
Temperature Rise: 98ºF to 140ºF
Size and Installation: 30"W x 13"H, Indoor, Pro install
Warranty and Support: 10yr heat exchanger, 5yr labor, 1yr parts
#10
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
Flow Rate (GPM): 5.9
Energy Efficiency: 99.8%
Fuel Type: Electric
Size and Installation: 17.63"W x 18.25"H x 3.5"D
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Buying Guide for the Best Tankless Hot Water Heaters
Choosing the right tankless hot water heater can significantly improve your home's energy efficiency and ensure you have a reliable supply of hot water. Unlike traditional water heaters that store hot water in a tank, tankless models heat water on demand, which can save space and reduce energy costs. To find the best fit for your needs, it's important to understand the key specifications and how they relate to your household's requirements.Flow Rate (GPM)Flow rate, measured in gallons per minute (GPM), indicates how much hot water the unit can produce at a given time. This is crucial because it determines whether the heater can meet your household's hot water demands. For example, a flow rate of 3-4 GPM is suitable for small households with one or two fixtures running simultaneously, while larger households with multiple fixtures may require a flow rate of 7-10 GPM. To choose the right flow rate, consider the number of people in your home and the number of hot water fixtures you expect to use at the same time.
Energy EfficiencyEnergy efficiency is measured by the unit's Energy Factor (EF) or Uniform Energy Factor (UEF). This spec indicates how efficiently the heater converts energy into hot water. Higher EF or UEF values mean better efficiency and lower energy costs. For example, a unit with an EF of 0.8 is less efficient than one with an EF of 0.95. To pick the right one, look for models with higher efficiency ratings, especially if you are concerned about reducing your energy bills and environmental impact.
Fuel TypeTankless water heaters can be powered by electricity, natural gas, or propane. The fuel type affects installation costs, operating costs, and performance. Electric models are typically easier to install and maintain but may have higher operating costs. Gas models, on the other hand, often provide higher flow rates and are more cost-effective in the long run but require proper ventilation and may have higher upfront installation costs. Choose the fuel type based on your existing infrastructure, availability of fuel sources, and long-term cost considerations.
Temperature RiseTemperature rise refers to the difference between the incoming water temperature and the desired output temperature. This spec is important because it affects the heater's ability to provide hot water in colder climates. For instance, if the incoming water temperature is 50°F and you want it heated to 120°F, the unit needs to handle a 70°F temperature rise. To choose the right model, consider the average temperature of your incoming water and ensure the heater can achieve the desired output temperature, especially during colder months.
Size and InstallationThe physical size of the tankless water heater and its installation requirements are important factors to consider. Tankless units are generally more compact than traditional tanks, but you still need to ensure you have enough space for installation. Additionally, some models may require specific venting or electrical upgrades. To pick the right size, measure the available space and check the installation requirements of the unit. If you have limited space or specific installation constraints, look for models designed for easy installation in tight spaces.
Warranty and SupportThe warranty and support offered by the manufacturer can provide peace of mind and protect your investment. Warranties typically cover parts and labor for a certain period, and longer warranties often indicate higher quality and reliability. To choose the right model, compare the warranty terms and consider the availability of customer support and service centers. Opt for a unit with a comprehensive warranty and good customer support to ensure you can get help if any issues arise.