The best gas instant water heater delivers an endless supply of hot water on demand, perfect for busy households and modern living. Choosing the right unit involves understanding your specific needs, such as the number of bathrooms, peak usage times, and desired temperature control. Opting for an undersized or inefficient model can lead to lukewarm showers, frustrating delays, and wasted energy, ultimately costing you more in the long run.
Factors like flow rate, energy efficiency ratings (U.S. Energy Star or equivalent), and venting requirements significantly impact performance and installation costs.
To help you make an informed decision, we’ve compiled a list of the top 10 best gas instant water heaters available, showcasing innovative features and robust reliability for consistent comfort.
For those seeking the best gas instant water heater, consider models offering high flow rates and robust BTU output, such as the Rheem RTG-84XLN-3, which delivers up to 8.4 GPM for 2-3 bathroom homes. Rinnai’s RX199iN also stands out for its versatility, allowing indoor or outdoor installation and operation on natural gas or propane.
Best Gas Instant Water Heaters at a Glance
| Image | Product | Buy |
|---|---|---|
Best Pick 1  | NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: Smart home ready | Check Price |
Best Pick 2  | Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water Best for: Outdoor efficiency focused | Check Price |
Best Pick 3  | Rinnai RE199iN Non-Condensing Natural Gas Tankless Water Heater, 199,000 BTU, Best for: Non-condensing basics | Check Price |
Best Pick 4  | Rinnai V53DeP Propane Tankless Water Heater, 5.3 GPM, Outdoor Installation Best for: Outdoor propane option | Check Price |
Best Pick 5  | Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Best for: Commercial installations | Check Price |
How We Picked
To determine the best gas instant water heater, we prioritized build quality, real-world performance, safety, durability, and standout features. Products like the Rinnai RX199iN and Rheem RTG-84XLN-3 impressed with their high GPM ratings and energy efficiency. We ruled out models lacking robust warranty information or those with lower BTU outputs that might struggle with demanding household needs.
Units offering flexible installation options, such as indoor/outdoor versatility, and advanced features like Smart Sense technology were given additional consideration, reflecting a commitment to user convenience and long-term value.
What Most Buyers Get Wrong
Matching BTU to Your Household Demand
Gas tankless water heaters are rated by BTUs (British Thermal Units), indicating their heating power. Higher BTU ratings mean more hot water capacity. For instance, a home with multiple bathrooms and high hot water usage, like running a dishwasher and shower simultaneously, will benefit from units with higher BTUs, such as the Rinnai RX199iN or Rheem RTG-84XLN-3, both offering powerful heating capabilities to prevent cold water sandwiches.
Understanding GPM for Simultaneous Use
Gallons Per Minute (GPM) is crucial for determining how many hot water fixtures your tankless heater can support at once. A 5.3 GPM unit like the Rinnai V53DeP is suitable for smaller homes or single-use scenarios, while homes needing to run two showers concurrently might require a higher GPM, like the 8.4 GPM offered by the Rheem RTG-84XLN-3 or the APUS 190,000 BTU heater, ensuring everyone gets hot water without interruption.
1. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
Best for: Condensing Smart Sense for flexible indoor/outdoor use.
This Rinnai RX199iN connects to either natural gas or propane, and can be installed indoors or outdoors, simplifying setup for various locations. Its Smart Sense gas control system adapts to your fuel source, providing consistent performance.
Delivering up to 11.1 GPM, this unit is sized like a small suitcase and provides hot water for up to 7 fixtures simultaneously. It operates at 120 volts with 98 watts and features a high efficiency rating of UEF .98.
Pros
- Handles 7 fixtures with 11.1 GPM flow rate
- Versa Vent allows indoor/outdoor installation
- Smart Sense gas control for natural gas or propane
- Compact size saves space
Cons
- Outdoor installation requires separate RX-OVC vent cap
Homeowners needing flexible fuel options and simultaneous fixture use will appreciate Rinnai’s adaptability. This unit is ideal for homes that require a reliable and efficient water heating solution in diverse installation scenarios.
2. Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water
Best for: Outdoor installation for 2-3 bathroom homes.
The Rheem RTG-84XLN-3 offers up to 8.4 GPM output, efficiently heating water for up to 3 bathrooms with its 180,000 BTU capacity. This natural gas unit is specifically designed for outdoor placement, ensuring durability and convenient installation.
Featuring Hot Start Programming, this non-condensing model minimizes cold water bursts and maintains a peak temperature of 140°F. It operates on 120 volts with 132 watts and is wall-mounted for a secure setup.
Pros
- Supplies 8.4 GPM for multiple fixtures
- Outdoor installation saves indoor space
- Hot Start Programming for consistent temperature
- 180,000 BTU heat output ensures rapid heating
Cons
- Fixed maximum temperature of 140°F
Ideal for homeowners with 2-3 bathrooms seeking robust hot water performance outdoors. This Rheem unit provides reliable heating for busy households during peak demand, all from an external installation.
3. Rinnai RE199iN Non-Condensing Natural Gas Tankless Water Heater, 199,000 BTU,
Best for: Energy efficient with LED display.
This Rinnai RE199iN non-condensing tankless water heater provides up to 9.8 GPM, heating water only when needed to reduce standby energy loss. Its compact, wall-mounted design includes an LED display that shows diagnostic codes for easier maintenance.
With a powerful 199,000 BTU output, this unit ensures endless hot water suitable for busy households. It operates at 199,000 watts and a maximum temperature of 140°F, delivering efficient on-demand performance.
Pros
- Delivers 9.8 GPM for continuous hot water
- On-demand heating saves energy
- Compact, space-saving wall-mounted design
- LED display with diagnostic codes simplifies maintenance
Cons
- Single fuel type: natural gas only
This Rinnai model is perfect for environmentally conscious homeowners who prioritize energy efficiency and easy upkeep. It’s designed for those needing a reliable, continuous hot water supply from a compact, user-friendly unit.
4. Rinnai V53DeP Propane Tankless Water Heater, 5.3 GPM, Outdoor Installation
Best for: Compact outdoor propane unit with Wi-Fi.
The Rinnai V53DeP propane tankless water heater offers 5.3 GPM, providing endless hot water for multiple appliances. Its energy-efficient design heats water on demand, enhancing the unit’s lifespan with improved scale detection features.
This compact outdoor unit is Wi-Fi capable, allowing for convenient monitoring. It utilizes 81 kilowatts for its heat output and a high-efficiency rating to conserve energy and deliver consistent hot water.
Pros
- 5.3 GPM flow rate for multiple needs
- Propane fuel source for diverse locations
- Wi-Fi capability for smart monitoring
- Enhanced scale detection improves longevity
Cons
- Lower flow rate suitable for fewer simultaneous uses
Homeowners with a propane connection seeking a compact, efficient outdoor water heater will find this Rinnai ideal. It’s suited for smaller to medium-sized households valuing on-demand hot water with smart features.
5. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane
Best for: Condensing Smart Sense for commercial or residential.
This Rinnai CX199iN condensing tankless water heater is compatible with both natural gas and propane and can be installed indoors or outdoors, thanks to its Versa Vent system. The Smart Sense gas control adapts to your fuel source, optimizing performance.
Providing up to 11.1 GPM, this unit is designed like a small suitcase, capable of supplying hot water to 7 fixtures simultaneously. It features a maximum temperature of 185°F and operates at 600 watts with a 96% efficiency rating.
Pros
- Handles 7 fixtures with 11.1 GPM flow rate
- Versa Vent allows indoor/outdoor installation
- Smart Sense gas control for natural gas or propane
- Higher maximum temperature of 185°F
Cons
- Outdoor installation requires separate RX-OVC vent cap
This Rinnai model is perfect for larger homes or commercial applications needing high flow rates and flexible fuel options. Its condensing technology and wide installation range make it a powerful choice for demanding hot water needs.
6. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water
Best for: High efficiency indoor natural gas installation.
The Rheem RTG-70DVLN-3 delivers up to 7.0 GPM, ideal for 2-3 bathroom homes that frequently use hot water. Its 160,000 BTU capacity ensures fast, reliable heating for showers and laundry, even during peak demand.
Designed specifically for indoor installation, this non-condensing natural gas unit features a durable, compact metal cabinet. It operates at 120 volts with 132 watts and includes an integrated digital display and Hot-start Programming.
Pros
- Supplies 7.0 GPM for busy households
- Indoor installation with a compact design
- Integrated digital display for easy use
- Hot-start Programming minimizes cold water bursts
Cons
- Fixed maximum temperature of 140°F
This Rheem unit is a solid choice for homeowners prioritizing an indoor installation with consistent hot water output for 2-3 bathrooms. Its efficient design ensures reliable performance for daily needs.
7. ThermoMate CZ422NG Natural Gas Tankless Water Heater, Up to 5
Best for: Precise temperature control for small homes.
The ThermoMate CZ422NG natural gas tankless water heater provides up to 5 GPM, heating water on-demand for simultaneous use of two showers. Its smart flow sensor and control chip adjust heating 20,000 times per second, ensuring ±1°F temperature consistency.
With a 113,000 BTU heat output, this unit ensures stable 105°F water temperature (based on 65°F inlet). It integrates 8 safety protections, including anti-freezing and dry combustion protection, operating at 120 volts.
Pros
- Precise ±1°F temperature consistency
- 5 GPM flow rate for multiple fixtures
- 8 integrated safety protections for reliability
- Smart flow sensor for optimal heating
Cons
- Lower BTU output may not be ideal for very high demand
This ThermoMate is perfect for small to medium-sized homes or apartments needing precise temperature control and reliable safety features. It’s designed for users who value comfort and consistent hot water without interruption.
8. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120
Best for: High flow rate with exclusive hot start.
The Rheem RTGH Series offers a flow rate of 0.4 – 8.4 GPM, ideal for homes with multiple hot water demands, such as simultaneous showers and laundry. Its 157,000 BTU output ensures rapid heating for consistent comfort.
With available temperature settings from 100 to 140°F (default 120°F), this unit features Exclusive Hot Start Programming to minimize cold water bursts. It operates on a fuel power source with electric ignition and 120 volts.
Pros
- 8.4 GPM flow rate for high demand
- Exclusive Hot Start Programming for consistent temps
- Wide temperature range from 100-140°F
- Electric ignition for reliable startup
Cons
- Covered by a 1-year labor warranty
This Rheem unit is best for families needing a high-performance water heater that can handle simultaneous use across several bathrooms. Its robust flow rate and smart temperature features make it a dependable choice.
9. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water
Best for: Outdoor liquid propane for 2-3 bathrooms.
The Rheem RTG-70XLP-3 delivers up to 7.0 GPM, efficiently heating water for 2-3 bathroom homes with its 160,000 BTU capacity. This liquid propane unit is designed for outdoor installation, featuring a durable metal cabinet for longevity.
This high-efficiency, non-condensing tankless water heater ensures fast, reliable hot water. It operates at 120 volts with 132 watts and includes Hot-start Programming to minimize cold water output. It features industry-best side-to-side clearance.
Pros
- Supplies 7.0 GPM for multiple fixtures
- Outdoor installation saves indoor space
- Liquid propane fuel source for flexibility
- Hot-start Programming for consistent temperature
Cons
- Fixed maximum temperature of 140°F
Ideal for homes that use liquid propane and require a reliable outdoor tankless water heater for 2-3 bathrooms. This Rheem model ensures consistent hot water supply during peak household demand.
10. APUS 190,000 BTU Outdoor Tankless Water Heater, 8.1 GPM Natural
Best for: Smart control and app for whole-home use.
The APUS 190,000 BTU outdoor tankless water heater provides 8.1 GPM, ideal for whole-house use by supplying 3 showers and 2 faucets simultaneously. Its ultra-low 0.79 GPM minimum flow ensures reliability even with weak water pressure.
Featuring app control via the Tuya APP and remote capabilities, this unit offers smart seasonal technology and advanced heat exchanger design. It operates at 120 volts and can reach a maximum temperature of 149°F.
Pros
- 8.1 GPM flow rate for whole-home coverage
- APP and remote control for smart adjustments
- Reliable startup with 0.79 GPM minimum flow
- Higher maximum temperature of 149°F
Cons
- Requires natural gas connection
This APUS tankless water heater is perfect for modern homes needing smart control and ample hot water for multiple simultaneous uses. Its ability to function with low water pressure makes it versatile.
Condensing vs. Non-Condensing: The Real Efficiency Divide
The most critical differentiator among these otherwise capable units isn’t ultimately flow rate or BTU output, but the fundamental technology: condensing versus non-condensing. For buyers prioritizing outright energy savings and a reduced environmental footprint over the long haul, the NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane and its ilk present a clear advantage, even if the upfront cost is higher.
Rinnai’s CX199iN Condensing Smart Sense Commercial Natural Gas or Propane, for example, captures exhaust heat that would otherwise vent into the atmosphere, using it to preheat incoming cold water. This process makes them significantly more efficient, potentially shaving 10-15% off your gas bill compared to their non-condensing counterparts like the Rheem RTG-84XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water or the Rinnai RE199iN Non-Condensing Natural Gas Tankless Water Heater, 199,000 BTU. While these latter units still offer substantial savings over traditional tanks, they are essentially leaving money on the table with every tank of hot water produced.
The trade-off, undeniably, is installation complexity and cost. Condensing units require a dedicated condensate drain line to handle the byproducts of this extra heat capture, and often necessitate higher-grade venting materials. This isn’t a small consideration, and for some installations, particularly in older homes or those with limited plumbing access, the added expense and labor might outweigh the marginal operational savings.
A Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water might be the simpler, more straightforward choice in such scenarios, as it avoids the condensate plumbing altogether.
Therefore, the savvy buyer of a best gas instant water heater needs to look beyond peak GPM and BTUs and assess their long-term energy goals, installation constraints, and willingness to invest for greater operational efficiency. The Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane is built for those who want the absolute best energy performance, while the Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water serves those who prioritize simplicity and immediate install cost.
What to Look for in a Best Gas Instant Water Heater
Flow rate and gallons per minute
To ensure your gas instant water heater can meet demand, understand its flow rate, measured in gallons per minute (GPM). A typical shower uses 2.5 GPM, while a faucet uses 1 GPM. For a household needing to run a shower and a sink simultaneously, aim for a unit with at least 5.5 GPM.
Lower-end models might offer 3-4 GPM, suitable for single-fixture use, while high-demand units can reach 9 GPM. Prioritize a 5.5 GPM or higher model for multi-fixture households; opt for 3 GPM if only one fixture will run at a time.
Temperature control and settings
Precise temperature control is crucial for comfort and safety. Look for units offering a wide range of adjustable temperatures, typically from 90°F to 140°F. Digital controls provide the most accuracy, allowing you to set specific temperatures down to the degree, which is ideal for households with children or elderly individuals.
Manual dial controls are less precise and can fluctuate more. Choose digital controls for ultimate temperature precision; select manual if slight variations are acceptable.
Energy efficiency and fuel consumption
Energy efficiency is directly tied to fuel consumption and long-term savings. Gas instant water heaters are rated by their Energy Factor (EF), with higher numbers indicating greater efficiency. An EF rating above 0.80 is considered good.
More efficient units will have lower gas consumption rates per gallon heated. Select a heater with an EF of 0.80 or higher for the best fuel economy; a rating below this will lead to higher operating costs.
Venting and installation requirements
Proper venting and installation are critical for safety and performance. Direct vent systems draw combustion air from outside and vent exhaust through a dedicated pipe, requiring specific clearances. Power vent systems use a fan to expel exhaust and can vent through walls or roofs, offering more installation flexibility.
For homes with limited ventilation options or a need for flexible placement, a power vent system is the superior choice. Always hire a qualified professional for installation.
Which Should You Choose?
- If you need an indoor or outdoor installation and want flexibility with fuel type, look for models with advanced venting and smart gas controls.
- If you have 2-3 bathrooms and frequent simultaneous hot water use, choose a unit with a high GPM (gallons per minute) and ample BTU output.
- If you prefer on-demand heating to save energy and have limited space, opt for a non-condensing model with a compact design.
- If you need to heat water for multiple appliances at once, especially for a busy household, prioritize a model with a higher GPM.
Quick Best Gas Instant Water Heater Buying Checklist
- Verify Flow Rate: Ensure the GPM (gallons per minute) meets your household’s peak demand for simultaneous hot water use.
- Check Temperature Range: Confirm the heater can reach your desired hot water temperature and offers precise control.
- Review Energy Efficiency: Look for higher Energy Factor (EF) ratings to minimize ongoing gas costs.
- Assess Venting Type: Understand if a direct vent or power vent system is compatible with your installation location.
- Consider Unit Size: Ensure the physical dimensions fit comfortably in your designated installation space.
- Confirm Ignition Type: Note whether the model uses electronic ignition or a pilot light, impacting energy use and reliability.
Frequently Asked Questions
What Is The Primary Benefit Of A Gas Tankless Water Heater?
The primary benefit of a gas tankless water heater is its continuous supply of hot water, meaning you’ll never run out during peak usage. These units heat water on demand, significantly reducing standby energy losses compared to traditional tank models.
How Does A Gas Instant Water Heater Differ From A Traditional Tank Model?
A gas instant water heater heats water only when a hot water faucet is turned on, providing an endless supply. Traditional tank models store and continuously heat a large volume of water, leading to potential energy waste and depletion of hot water.
What Gpm Is Generally Sufficient For A Household?
For most households, a GPM (gallons per minute) of 6.0 to 9.0 is generally sufficient, especially if multiple hot water fixtures might be used simultaneously. This flow rate allows for comfortable showering and dishwashing without interruption.
Are Gas Instant Water Heaters More Energy-Efficient?
Yes, gas instant water heaters are typically more energy-efficient because they only heat water when needed, eliminating standby energy losses. This on-demand heating significantly reduces fuel consumption over time compared to tank-based systems.
What Are The Installation Considerations For A Gas Instant Water Heater?
Installation considerations include adequate gas line size, proper ventilation for exhaust gases, and the need for a dedicated electrical connection for models with electronic controls. Professional installation is highly recommended for safety and optimal performance.
Final Words
In conclusion, opting for the best gas instant water heater offers significant advantages in continuous hot water supply and energy savings. Its on-demand heating technology provides reliable comfort for your entire household while reducing utility costs. Investing in an efficient unit will enhance your home’s functionality and provide peace of mind for years to come.
