The best tankless water heater system provides efficient, on-demand hot water, ideal for homeowners seeking energy savings and consistent comfort. Choosing the right unit involves considering flow rate, fuel type (gas vs. electric), and space requirements, as a mismatch can lead to inadequate hot water or inefficient operation.
Factors like hard water compatibility and venting needs also play a crucial role in long-term performance and system lifespan. To help you navigate the market and find a reliable solution, we’ve compiled a list of the top 10 tankless water heater systems available, ensuring you get premium performance and lasting value for your household’s hot water needs.
The best tankless water heater system balances efficiency with flow rate for consistent hot water. For whole-house applications needing up to 4.2 GPM, the Westinghouse 18kW Electric Tankless Water Heater is a strong contender, providing enough hot water for 2-3 fixtures simultaneously without temperature drops. Gas options, such as the Rinnai RX199iN, offer versatility for indoor/outdoor installation and are suitable for propane or natural gas.
Our Best Tankless Water Heater System Picks
| Image | Product | Buy |
|---|---|---|
Best Pick 1  | NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: Condensing gas luxury | Check Price |
Best Pick 2  | Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY Best for: Small apartment electric | Check Price |
Best Pick 3  | Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray Best for: High-flow electric | Check Price |
Best Pick 4  | Westinghouse Tankless Water Heater Electric 14kW 240V, Instant On-Demand Hot Best for: Compact electric setup | Check Price |
Best Pick 5  | Westinghouse 18kW Electric Tankless Whole House Water Heater, 4.2 GPM Best for: Whole house power | Check Price |
How We Picked
To identify the best tankless water heater system, we rigorously evaluated popular models like the Rinnai RX199iN and Rheem RTEX-We prioritized build quality and durability, examining materials and construction for long-term performance. Real-world performance, including GPM flow rates and heating speed, was crucial, differentiating units like the Westinghouse 18kW from lower-output options.
Safety features and outstanding capabilities, such as the Rinnai’s indoor/outdoor versatility and smart technology in the Electrolux 14kW, were also key. Models failing to meet our high standards for efficiency or essential features were ruled out, ensuring a curated selection.
What Most Buyers Get Wrong
Understanding GPM for Your Hot Water Needs
When choosing a tankless water heater, Gallons Per Minute (GPM) is crucial. It tells you how much hot water the unit can deliver at any given moment. For example, the Rheem RTG-84XLN-3 offers 8.4 GPM, ideal for simultaneous use of multiple fixtures, while the Rheem RTEX-13 provides 13kW (which equates to a lower GPM for electric models).
Consider your household’s peak usage – a simultaneous shower and dishwasher run demands a higher GPM than just a single faucet.
Gas vs. Electric: Powering Your Endless Hot Water
Deciding between gas and electric tankless water heaters is a key consideration. Gas models like the Rinnai RX199iN or Rheem RTG-70DVLN-3 often boast higher GPMs, meaning more simultaneous hot water, but require a gas line. Electric units, such as the Westinghouse 14kW or Electrolux 14kW, offer simpler installation in many cases but may have limitations on GPM depending on your home’s electrical capacity, and require significant amperage like the Rheem RTEX-24 needing three 40 AMP breakers.
1. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
Best for: Versatile indoor/outdoor gas unit.
This Rinnai RX199iN unit’s Smart Sense gas control system allows operation with either natural gas or propane, offering significant installation flexibility. Its compact, suitcase-sized design belies its powerful performance, providing up to 11.1 GPM for simultaneous fixture use.
With a high heat output of 199,000 BTU and an efficiency rating of UEF .98, this condensing unit can power approximately 7 fixtures at once. It supports both indoor and outdoor installations, and its voltage is 120 Volts.
Pros
- Dual fuel capability (NG/Propane)
- Up to 11.1 GPM flow rate
- Compact size
- Smart Home Compatible
Cons
- Outdoor installation requires an additional RX-OVC vent cap.
This Rinnai model is ideal for homeowners seeking a flexible gas tankless water heater. Its ability to run on two fuel types makes it a strong contender for diverse installation environments.
2. Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
Best for: Compact electric heater for single points.
The Rheem RTEX-13 offers precise temperature control with its external digital thermostatic control, allowing adjustments in 1-degree Fahrenheit increments. Its dual copper heating elements ensure durability and are field serviceable, contributing to long-term reliability.
This 13kW electric unit operates at 240 Volts and delivers a flow rate of 4.8 GPM, making it suitable for multiple low-demand fixtures. It boasts an impressive 99.8% energy efficiency and features a digital LED display for easy monitoring.
Pros
- 99.8% energy efficiency
- Precise 1°F temperature control
- Durable copper heating elements
- Simple installation with included adapters
Cons
- Flow rate of 4.8 GPM may be insufficient for simultaneous high-demand uses.
This Rheem electric heater is best for apartments or smaller homes needing on-demand hot water for a few fixtures. Its precise temperature control is a significant advantage.
3. Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
Best for: Whole-home electric for larger needs.
The Rheem RTEX-24 is built to deliver continuous hot water for busy households, with a 24kW power output designed for whole-home applications. Its high-efficiency operation means minimal energy waste while providing the hot water needed, even in colder climates if the household service can support it.
This 240-volt electric unit provides a flow rate of 5.9 GPM, capable of handling several fixtures simultaneously. It requires three 40-amp double-pole breakers and recommends a 200-amp household service for optimal performance, ensuring ample power supply.
Pros
- 5.9 GPM flow rate for multiple fixtures
- 24kW power for whole-home use
- 99.8% energy efficiency
- LED display for temperature monitoring
Cons
- Requires significant electrical infrastructure: three 40A breakers and 200A service.
This Rheem model is an excellent choice for larger homes or those with high simultaneous hot water demand. Its substantial power output ensures continuous supply.
4. Westinghouse Tankless Water Heater Electric 14kW 240V, Instant On-Demand Hot
Best for: Compact electric for small demands.
With a 14kW heating system, the Westinghouse electric tankless water heater provides immediate hot water upon demand, featuring a starting flow rate as low as 0.5 GPM. This unit is designed for efficiency, drawing power only when hot water is needed, reducing standby energy loss.
This 240V model delivers a maximum flow rate of 3.38 GPM, suitable for single-fixture applications or low-demand simultaneous use. It requires a dedicated 60-amp double-pole circuit breaker and uses 6 AWG wire for safe and efficient operation.
Pros
- Instant hot water delivery
- Low starting flow rate (0.5 GPM)
- Compact 14kW design
- ETL Certified for safety
Cons
- Maximum flow rate of 3.38 GPM limits simultaneous use of multiple high-demand fixtures.
This Westinghouse electric unit is suitable for small apartments, RVs, or as a point-of-use heater for specific applications. Its instant heating capability is a key benefit.
5. Westinghouse 18kW Electric Tankless Whole House Water Heater, 4.2 GPM
Best for: Smart electric for whole-house needs.
This Westinghouse 18kW electric tankless water heater delivers up to 4.2 GPM, providing enough hot water for 2-3 fixtures concurrently. Its Smart WiFi control allows for remote adjustments via smartphone app or voice commands with Alexa and Google Assistant, offering convenience and modern functionality.
Operating at 240 Volts, this unit features copper heating elements for efficient heat transfer and durability. It’s designed for whole-house applications, ensuring continuous hot water on demand. The unit’s maximum temperature can be set up to 140°F.
Pros
- 4.2 GPM flow rate for multiple fixtures
- Smart WiFi and voice control
- Copper heating elements
- 18kW power suitable for whole-house
Cons
- Requires significant electrical supply; 18kW necessitates careful circuit planning.
This Westinghouse model is an excellent choice for households seeking a smart, whole-house electric tankless water heater. Its app control adds a layer of modern convenience.
6. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water
Best for: High-efficiency gas for 2-3 bathrooms.
The Rheem RTG-70DVLN-3 is a high-efficiency non-condensing tankless gas water heater that delivers up to 7.0 GPM, perfect for homes with 2-3 bathrooms. Its natural gas operation with 160,000 BTUs ensures fast and reliable hot water delivery, even during peak usage times.
Designed for indoor installation, this unit features a durable metal cabinet and supports easy wall mounting. It operates on 120 Volts and includes features like Hot-start Programming to minimize cold water bursts. Gas line compatibility is 1/2 inch.
Pros
- 7.0 GPM flow rate for multiple needs
- 160,000 BTU heat output
- High energy efficiency
- Hot-start programming
Cons
- Requires natural gas line and proper venting for indoor installation.
This Rheem natural gas unit is ideal for homeowners looking for a reliable tankless system for medium-sized homes. Its fast heating and efficiency are key benefits.
7. Electrolux 14kW Tankless Water Heater Electric 240V – Smart WiFi
Best for: Smart electric for 1-2 fixtures.
Electrolux’s 14kW electric tankless water heater provides instant hot water in as little as 3 seconds from its 240V system, designed for 1-2 fixtures. The Smart WiFi and Alexa voice control features allow for convenient temperature adjustments and monitoring from anywhere.
With a maximum flow rate of 3.4 GPM, this unit provides a comfortable hot water experience for showers and sinks. It comes with a scale inhibitor to help maintain performance and is ETL Certified, ensuring safety standards are met.
Pros
- Instant hot water (3 seconds)
- Smart WiFi and voice control
- 3.4 GPM flow rate for 1-2 fixtures
- Includes scale inhibitor
Cons
- 14kW power output is best suited for limited simultaneous fixture use.
This Electrolux model is a great choice for smaller households or apartments needing quick, on-demand hot water with modern smart features. The voice control adds significant convenience.
8. Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water
Best for: High-volume gas for larger homes.
The Rheem RTG-84XLN-3 delivers an impressive 8.4 GPM flow rate, powered by natural gas with 180,000 BTUs, making it suitable for larger homes with 2-3 bathrooms and high hot water demands. Its high-efficiency, non-condensing design ensures consistent performance and reliability.
This unit is designed for outdoor installation, featuring a durable metal cabinet. It operates on 120 Volts and includes Hot-start Programming to reduce the delay in receiving hot water. Overheat protection adds an extra layer of safety.
Pros
- 8.4 GPM flow rate for high demand
- 180,000 BTU heat output
- Designed for outdoor installation
- Hot Start Programming
Cons
- Outdoor installation required, limiting placement options.
This Rheem outdoor gas unit is ideal for larger residences or homes with multiple bathrooms requiring significant hot water capacity simultaneously. Its high flow rate is a major advantage.
9. Westinghouse Smart Tankless Water Heater Gas Indoor, 7.9 GPM 180,000
Best for: Smart gas for whole-house and control.
The Westinghouse Smart Tankless Water Heater offers continuous hot water for up to 3-5 fixtures simultaneously with its 7.9 GPM flow rate and 180,000 BTU output. Its Smart WiFi app control allows users to easily adjust the water temperature and monitor operation remotely.
This indoor gas unit operates on 120 Volts and provides precise temperature control within ±1°F. It is designed for whole-house use, supporting showers, laundry, and dishwashing needs without interruption. Overheat protection ensures safe operation.
Pros
- 7.9 GPM flow rate for whole-house
- Smart WiFi app control
- ±1°F temperature control
- 180,000 BTU heat output
Cons
- Requires natural gas line and proper venting for indoor installation.
This Westinghouse smart gas tankless water heater is excellent for families needing consistent hot water and remote control capabilities. Its high flow rate handles substantial demand.
10. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane
Best for: Commercial-grade condensing gas unit.
The Rinnai CX199iN is a condensing Smart Sense commercial-grade tankless water heater, capable of operating on either natural gas or propane, with installation flexibility for indoor or outdoor use. It provides an impressive 11.1 GPM, suitable for high-demand applications.
This unit has a heat output of 199,000 BTU and an efficiency of 96%, offering robust performance for multiple fixtures simultaneously. It operates on 120 Volts and can reach a maximum temperature of 185°F, meeting demanding hot water needs.
Pros
- Up to 11.1 GPM flow rate
- Dual fuel capability (NG/Propane)
- Suitable for indoor/outdoor installation
- High maximum temperature (185°F)
Cons
- Condensing unit requires a specific venting setup.
This Rinnai commercial-grade unit is ideal for businesses or large homes with very high hot water usage. Its condensing technology and dual-fuel option offer efficiency and flexibility.
Gas vs. Electric: The BTU Fallout
When selecting a best tankless water heater system, the ultimate deciding factor is the BTU output, not the kilowatt rating, because it directly dictates simultaneous fixture capacity.
The distinction between gas and electric tankless heaters is not merely about power source; it’s about raw heating potential delivered under real-world demand. While electric units like the Rheem RTEX-13 Heating Chamber or the Westinghouse 14kW Electric Tankless Water Heater offer convenient, compact solutions, their kilowatt ratings translate to inherent limitations in flow rate. The Westinghouse 14kW, for instance, maxes out at a respectable 3.38 GPM, suitable for a single low-demand fixture but struggling under the load of concurrent needs.
The Rheem RTEX-24 24kW Electric Tankless Water Heater offers more power at 24kW, forcing a substantial 3 x 40 AMP breaker requirement and demanding a robust 200 AMP household service, a significant installation hurdle many homeowners overlook. This highlights a critical trade-off: electric models often require substantial electrical infrastructure upgrades to achieve even moderate flow rates, whereas gas units leverage a more readily available energy source to deliver significantly higher BTUs.
Consider the gas offerings: the Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Heater, powered by 160,000 BTUs, efficiently handles up to 7.0 GPM, suitable for multiple bathrooms. Stepping up, the Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water Heater delivers an impressive 8.4 GPM with 180,000 BTUs, catering to larger households. Similarly, the Westinghouse Smart Tankless Water Heater Gas Indoor, also rated at 180,000 BTU, boasts 7.9 GPM, reinforcing the higher flow achievable with gas.
Even the versatile Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane and Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane, with their One Model, Anywhere installation flexibility, are fundamentally designed around the higher BTUs characteristic of gas combustion, enabling significantly greater hot water delivery than their electric counterparts without demanding extensive electrical system overhauls.
Ultimately, if your home requires simultaneous hot water delivery across multiple fixtures—a shower running while dishes are being washed, for example—the BTU output of a natural gas unit like the Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water Heater is the non-negotiable spec to prioritize over the inflated kilowatt figures of electric alternatives.
What to Look For in a Best Tankless Water Heater System
Fuel source: gas vs electric considerations
The energy source you choose for your tankless water heater dictates installation requirements and ongoing operational considerations. Natural gas and propane models, such as the Rinnai RX199iN and Rheem RTG-84XLN-3, leverage your existing gas line and typically offer robust hot water output, with the latter delivering up to 8.4 GPM. These units, often powered by 160,000 to 180,000 BTUs, are well-suited for homes with multiple simultaneous hot water demands.
Conversely, electric tankless water heaters, like the Rheem RTEX-24 which requires three 40-amp double-pole breakers, demand substantial electrical capacity. Models like the Westinghouse Electric 14kW have a maximum flow rate of 3.38 GPM and a current draw of 59A, necessitating a dedicated 60-amp circuit.
For whole-house solutions, the Westinghouse 18kW Electric Tankless Whole House Water Heater can supply 2-3 fixtures concurrently. The initial setup and the continuous availability of your chosen fuel will heavily influence your decision.
Water flow rate gpm for simultaneous use
A tankless water heater’s ability to supply hot water to multiple points of use simultaneously is often measured in gallons per minute (GPM). You can’t just assume any unit will keep up with a busy household; a unit like the Westinghouse 18kW Electric Tankless Whole House Water Heater, rated at 4.2 GPM, is designed to supply 2-3 fixtures concurrently without a temperature drop. For more demanding scenarios involving 2-3 bathrooms and simultaneous usage like showers and laundry, consider models with higher flow rates, such as the Rheem RTG-70DVLN-3 at 7.0 GPM or the Westinghouse Smart Tankless Water Heater Gas Indoor, which boasts an impressive 7.9 GPM.
For even greater capacity, the Rheem RTG-84XLN-3 offers up to 8.4 GPM. Electric models like the Westinghouse Tankless Water Heater Electric 14kW (3.38 GPM) are suitable for fewer fixtures, while units with modulating power, such as the Rheem 240V Heating Chamber RTEX-13, can better adapt to varying demand, ensuring hot water availability when you need it most.
Condensing vs noncondensing technology
Gas tankless water heaters can be broadly categorized as condensing or non-condensing, a distinction directly impacting their energy efficiency and venting requirements. Condensing models, like the Rinnai RX199iN and Rinnai CX199iN, capture extra heat from exhaust gases that would otherwise be lost, leading to significantly higher efficiency ratings compared to their non-condensing counterparts. This captured heat condenses water vapor in the exhaust, hence the name, and may require a condensate drain line.
Non-condensing units, such as the Rheem RTG-70DVLN-3 and Rheem RTG-84XLN-3, achieve high efficiency through advanced burner technology and up to 8.4 GPM flow rates but do not recapture this latent heat. When deciding, consider that while condensing units offer superior energy savings over their lifespan, their initial installation might involve more complex venting and potentially a condensate management system.
Non-condensing options, on the other hand, often present a simpler installation and may be suitable for homes prioritizing straightforward setup, even if they trade a percentage of energy efficiency for that convenience.
Installation location flexibility
The physical space available for a water heater significantly influences the type and model you’ll choose. Some tankless units offer remarkable installation flexibility, allowing placement in a wider array of locations. Take, for instance, the Rinnai RX199iN and CX199iN models, which are specifically designed for installation either indoors or outdoors thanks to their Versa Vent technology.
This adaptability can be a game-changer if your primary installation spot has limited space or ventilation challenges. Conversely, many electric tank
Electrical requirements for electric models
Electric tankless water heaters draw a significant amount of power, and understanding their electrical requirements is crucial for safe and efficient operation. For instance, the Rheem RTEX-24 24kW model demands a robust setup, requiring three 40-amp double-pole breakers and recommending a 200-amp household service to accommodate its substantial power draw. Other models have different needs; the Westinghouse 14kW unit, while still powerful, can operate on a single 60-amp double-pole circuit.
Even within similar wattage, amperage requirements can vary; the Westinghouse 18kW model, designed for whole-house use, will naturally necessitate a higher amperage capacity than its 14kW counterpart, though a specific breaker size isn’t detailed. Beyond raw power, some advanced electric units, like the Electrolux 14kW Smart WiFi model, integrate smart features that also rely on a stable electrical connection for connectivity.
Always verify your home’s existing electrical capacity and consult with a qualified electrician to ensure proper installation and prevent overloading your system.
Quick Best Tankless Water Heater System Buying Checklist
- Fuel Type: Choose between natural gas, propane, or electric based on your home’s existing utilities and cost-effectiveness.
- Flow Rate (GPM): Calculate your peak hot water demand by adding the GPM of all fixtures that might run simultaneously to ensure sufficient output.
- Temperature Rise: Select a heater with a temperature rise capacity that matches your incoming water temperature and desired output temperature, especially crucial for colder climates.
- Energy Efficiency (UEF): Look for a high Uniform Energy Factor (UEF) rating, indicating less energy consumption and lower operating costs year-round.
- Brand Reputation & Warranty: Research established brands known for reliability and check warranty periods for peace of mind and potential long-term support.
- Venting Requirements: Understand the venting needs of the unit (e.g., direct vent, power vent, unvented) and assess if your installation location can accommodate them.
Frequently Asked Questions
What Are The Key Benefits Of Switching To A Tankless Water Heater System?
Switching to a tankless water heater system offers significant benefits primarily centered around energy efficiency and continuous hot water availability. These units heat water on demand, eliminating standby energy losses associated with traditional tank heaters and providing an endless supply for your household needs.
How Much Will A High-Quality Tankless Water Heater System Typically Cost To Install And Operate?
A high-quality tankless water heater system typically costs between **$3,000 and $6,000** to install, with ongoing operating costs significantly lower than traditional tank heaters. This price range reflects the unit’s advanced technology and the specialized venting and gas line modifications often required for proper integration.
Which Type Of Tankless Water Heater, Gas Or Electric, Is Best Suited For My Home’S Needs?
Gas tankless water heaters are generally best suited for homes with higher hot water demand due to their faster heating capabilities and continuous hot water supply. Electric tankless models are a good choice for smaller homes or supplemental applications where consistent, high-volume hot water isn’t consistently needed.
Are There Specific Features I Should Look For To Ensure A Tankless Water Heater System Is Energy-Efficient?
Yes, energy-efficient tankless water heaters possess specific features like a high Energy Factor (EF) rating or Uniform Energy Factor (UEF) rating. Look for models with a UEF of 0.82 or higher, indicating superior energy performance by minimizing heat loss during operation and maximizing hot water output relative to energy input.
Can A Tankless Water Heater System Reliably Supply Hot Water For Multiple Showers And Appliances Simultaneously In A Busy Household?
Yes, a properly sized tankless water heater system can reliably supply hot water for multiple showers and appliances simultaneously in a busy household. The key factor is selecting a unit with a sufficient flow rate (gallons per minute) to meet the peak simultaneous demand of all fixtures and appliances operating at once.
Final Words
Embrace the future of home water heating with a top-tier tankless water heater system. Experience on-demand hot water, exceptional energy savings, and a more efficient home, all while freeing up valuable space. Investing in this technology isn’t just an upgrade; it’s a smart move towards sustained comfort and reduced utility bills.
Make the switch today and enjoy the continuous flow of hot water you deserve.
