Imagine never running out of hot water again, no matter how many showers, loads of laundry, or dishwashing cycles you need to tackle in a day. Gas tankless water heaters deliver exactly that—unlimited hot water on demand, while saving space and energy compared to traditional tank units.
But with so many models on the market, choosing the right one can feel overwhelming. This guide breaks down the top gas tankless water heaters, highlighting their key features, benefits, and ideal use cases to help you find the perfect fit for your home and lifestyle.
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Novieex Natural Gas Tankless Water Heater, Indoor Max 4.3 GPM, 100,000 BTU
Best forSmall homes and point-of-use
- Precise temperature control
- Compact size
ConsiderLower flow rate
ThermoMate CZ422NG, Natural Gas Tankless Water Heater Indoor, Up to 5 GPM
Best forFamilies with two showers
- Handles two showers
- Eight safety protections
ConsiderTemperature range limited
Rinnai RX199iN Condensing Smart Sense Tankless Water Heater
Best forFlexible indoor or outdoor installation
- Indoor or outdoor installation
- Dual fuel capability
ConsiderProfessional installation required
Rheem RTG Series 8.4 GPM Natural Gas Tankless Water Heater Outdoor | 180,00…
Best forLarge families, multi-bathroom homes
- High flow rate
- Energy efficient
ConsiderOutdoor only
Ranein Propane Gas Tankless Water Heater, Indoor Max 8.5 GPM, 190,000 BTU I…
Best forHigh-demand propane applications
- High flow rate
- Underneath fan for safety
ConsiderPropane only
Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater Indoor | 160,000…
Best forIndoor replacement for tank heaters
- Energy efficient
- Indoor installation
ConsiderLower flow than 8.4 GPM model
Westinghouse Tankless Water Heater Gas Indoor, 7.9 GPM 180,000 BTU
Best forSmart home integration
- WiFi and voice control
- Precise temperature stability
ConsiderRequires WiFi setup
Ranein Propane Gas Tankless Water Heater, Indoor Max 3.6 GPM, 80,000 BTU In…
Best forCompact spaces and cabins
- Compact size
- Double heating chamber
ConsiderLower flow rate
APUS Natural Gas Tankless Water Heater 140,000 BTU Indoor Installation Up t…
Best forInstant hot water with smart control
- Zero cold water technology
- Built-in booster pump
ConsiderRequires WiFi for smart features
Ranein Propane Gas Tankless Water Heater, Indoor Max 4.3 GPM, 100,000 BTU I…
Best forVersatile preset temperature modes
- Four preset modes
- Wide temperature range
ConsiderPropane only
Novieex Natural Gas Tankless Water Heater – Compact and Precise
Brand: NOVIEEX
A reliable, compact option for smaller households needing consistent hot water.
The Novieex Natural Gas Tankless Water Heater is a solid choice for smaller homes or point-of-use applications. With a 100,000 BTU output and a maximum flow rate of 4.3 GPM, it can comfortably handle a shower and a kitchen faucet simultaneously. The unit maintains water temperature within ±1°F, so you won’t experience sudden cold or hot spikes while you’re in the middle of a shower.
Installation is straightforward with standard NPT 1/2-inch connections, and it operates on standard 110V-120V AC power. The temperature range is wide, from 95°F to 149°F, giving you flexibility for different needs. Its compact size makes it easy to fit in tight spaces, and the digital thermostat allows for precise adjustments. If you’re looking for an efficient, no-frills unit for a small household, this one delivers.
- Precise temperature control
- Compact size
- Easy installation
- Lower flow rate
- Requires electrical connection
ThermoMate CZ422NG – Dual Shower Power
Brand: thermomate
A dependable choice for households needing simultaneous hot water for two showers.
The ThermoMate CZ422NG is engineered to handle two showers at once, delivering up to 5 GPM with its 113,000 BTU burner. It maintains a stable 105°F output even with a 65°F inlet temperature, ensuring a comfortable experience for multiple users. The unit features eight safety protections, including boil-dry, freeze, and flame-out safeguards, giving you peace of mind.
Its heat exchanger is made from oxygen-free copper, which offers superior thermal conductivity and corrosion resistance compared to standard materials. The smart diagnostic display lets you easily adjust the temperature between 90°F and 140°F and monitor flow. This model is an excellent mid-range option for families who need reliable hot water without the high cost of premium units.
- Handles two showers
- Eight safety protections
- Oxygen-free copper exchanger
- Temperature range limited
- Requires venting
Rinnai RX199iN – Smart and Versatile Condensing Unit
Brand: Rinnai
A versatile, high-efficiency unit that adapts to your home's needs.
The Rinnai RX199iN stands out with its versatility: it can be installed indoors or outdoors thanks to the Versa Vent system, and it runs on either propane or natural gas with a simple conversion. This condensing unit is compact, about the size of a small suitcase, yet delivers high efficiency and endless hot water. The smart design includes an easy-to-use interface and a Quick Flush feature that simplifies maintenance.
With its super-high energy efficiency, this model can significantly reduce your utility bills. The RX199iN is ideal for homeowners who want flexibility in installation and fuel type. Professional installation is recommended, but the long-term savings and convenience make it a worthwhile investment. If you’re looking for a top-tier, smart tankless water heater, this Rinnai model is a premium choice.
- Indoor or outdoor installation
- Dual fuel capability
- High efficiency
- Professional installation required
- Premium price
Rheem RTG Series 8.4 GPM – Whole-House Power
Brand: Rheem
A robust, energy-saving solution for whole-house hot water needs.
The Rheem RTG Series 8.4 GPM is a powerhouse designed for large families and multi-bathroom homes. With 180,000 BTUs and a flow rate of 8.4 GPM at a 35°F temperature rise, it delivers endless hot water for simultaneous use across multiple fixtures. This non-condensing unit boasts a 0.82 Uniform Energy Factor (UEF), saving up to 34% on energy costs compared to a 50-gallon electric tank heater.
Outdoor installation frees up indoor space, and the durable construction ensures long-lasting performance. The digital LED display makes temperature adjustments easy, and the unit is CSA certified for safety. If you have a large household with high hot water demand, this Rheem model is a reliable workhorse that won’t let you down.
- High flow rate
- Energy efficient
- Outdoor installation saves space
- Outdoor only
- Non-condensing design
Ranein Propane 8.5 GPM – High Capacity with Safety
The Ranein Propane Tankless Water Heater delivers an impressive 8.5 GPM with 190,000 BTUs, making it suitable for up to four water points simultaneously. Its unique fan placement underneath enhances safety by preventing smoke backflow, and the blower automatically adjusts speed based on demand for optimal combustion. This unit eliminates the need for preheating, providing unlimited hot water instantly.
Installation is straightforward with standard 3/4-inch NPT connections, and its compact size (24.25″L x 15.08″W x 8.07″H) saves valuable space. The high heating capacity ensures you’ll never run out of hot water, even during peak usage. This model is perfect for larger homes or workshops where propane is the fuel of choice.
- High flow rate
- Underneath fan for safety
- Compact design
- Propane only
- May require professional installation
Rheem RTG Series 7.0 GPM – Indoor Efficiency
Brand: Rheem
A solid indoor option for medium-sized households seeking efficiency.
The Rheem RTG Series 7.0 GPM is tailored for indoor installation, providing 160,000 BTUs and a flow rate of 7.0 GPM at a 35°F temperature rise. It’s ideal for homes with 2-3 water points running simultaneously, such as a shower, kitchen sink, and laundry. With a 0.82 UEF, it saves up to 34% on energy costs compared to traditional tank heaters.
This non-condensing unit is CSA certified and features advanced safety protections. The digital LED display allows for easy temperature monitoring and adjustments. As a perfect replacement for aging tank water heaters, this Rheem model offers reliable, endless hot water while reducing your carbon footprint. If you need a dependable indoor unit, this is a strong contender.
- Energy efficient
- Indoor installation
- Reliable performance
- Lower flow than 8.4 GPM model
- Non-condensing
Westinghouse 7.9 GPM – Smart WiFi and Voice Control
Brand: Westinghouse
A feature-rich, smart tankless water heater for modern homes.
The Westinghouse Tankless Water Heater combines high performance with smart technology. Delivering up to 7.9 GPM and 180,000 BTUs, it ensures endless hot water for showers, laundry, and dishwashing. What sets it apart is its smart WiFi app and voice control, allowing you to adjust temperature and monitor operation from anywhere using your smartphone or voice commands.
The unit maintains water temperature within ±1°F thanks to advanced self-modulating technology, which automatically adjusts gas and water flow. This not only provides comfort but also enhances energy efficiency by heating water only when needed. The Westinghouse is perfect for tech-savvy homeowners who want convenience and control at their fingertips.
- WiFi and voice control
- Precise temperature stability
- High flow rate
- Requires WiFi setup
- Premium price
Ranein Propane 3.6 GPM – Compact and Efficient
The Ranein Propane Tankless Water Heater is a compact unit with 80,000 BTUs and a flow rate of 3.6 GPM, supporting 2-3 water points simultaneously. Its precision temperature control ranges from 95°F to 149°F, with a high-temperature lock for safety. The double heating chamber design boosts efficiency and ensures uniform temperature, while also operating quieter than standard units.
The oxygen-free copper heat exchanger enhances heat transfer and resists corrosion, promising durability. This model is ideal for small apartments, cabins, or as a point-of-use heater. Its energy-saving features and compact footprint make it an excellent choice for those with limited space but a need for reliable hot water.
- Compact size
- Double heating chamber
- Energy efficient
- Lower flow rate
- Propane only
APUS Natural Gas – Zero Cold Water Technology
Brand: APUS
An innovative unit that delivers instant hot water with smart convenience.
The APUS Natural Gas Tankless Water Heater features exclusive single-circulation technology that eliminates cold water wait time, delivering instant hot water. With 140,000 BTUs and a built-in booster pump that increases water flow by up to 130%, it achieves a maximum of 6.8 GPM, easily supporting two showers and two sinks running simultaneously without temperature fluctuations.
The unit uses a durable oxygen-free copper heat exchanger and a bottom turbo fan design that operates 30% quieter than standard models. Advanced safety features provide peace of mind. The smart WiFi app control allows you to adjust settings remotely. This model is perfect for homeowners who value instant hot water and smart connectivity.
- Zero cold water technology
- Built-in booster pump
- Quiet operation
- Requires WiFi for smart features
- Higher upfront cost
Ranein Propane 4.3 GPM – Preset Modes for Convenience
Brand: Ranein
A user-friendly propane heater with convenient preset modes for everyday use.
The Ranein Propane Tankless Water Heater offers 100,000 BTUs and a flow rate of 4.3 GPM, supporting 3-4 water points. Its standout feature is the four intelligent preset modes: 4-season, Kitchen, Bathtub, and Shower. With one click, you can switch between modes, with the 4-season mode auto-matching temperature and kitchen defaulting to 100°F for convenience.
Precision temperature control ranges from 95°F to 155°F, and a high-temperature lock prevents scalding, making it safe for kids and elders. The oxygen-free copper heat exchanger enhances efficiency and durability. This model is ideal for households that want versatile, easy-to-use temperature settings without complex programming.
- Four preset modes
- Wide temperature range
- High-temp lock safety
- Propane only
- Medium flow rate
Buyer’s Guide: What to Consider
Choosing the right gas tankless water heater involves balancing performance, efficiency, and your household’s specific needs. Here are key factors to consider before making a purchase.
- Flow Rate (GPM): Determine your peak hot water demand by counting fixtures you might use simultaneously. A typical shower uses 2-3 GPM, so a 4.3 GPM unit handles one shower plus a sink, while 8+ GPM units support multiple showers and appliances.
- BTU Output: Higher BTU ratings mean faster heating and higher flow rates, especially in colder climates where incoming water temperature is lower. Choose a unit with sufficient BTUs to meet your needs without oversizing, which wastes energy.
- Fuel Type: Decide between natural gas and propane based on your home's availability. Natural gas is common in urban areas, while propane is ideal for rural homes or cabins. Some models offer dual fuel capability for flexibility.
- Indoor vs. Outdoor Installation: Indoor units require proper venting to expel combustion gases, while outdoor units save indoor space but must withstand weather. Consider your climate and installation location when choosing between the two.
- Energy Efficiency: Look for a high Uniform Energy Factor (UEF) to maximize savings. Condensing units are more efficient than non-condensing, but they cost more upfront. Evaluate your usage to determine the payback period.
Conclusion
Selecting the best gas tankless water heater depends on your home’s size, hot water demand, and fuel availability. For large families, the Rheem RTG Series 8.4 GPM or Ranein 8.5 GPM offer high capacity. Smart features like WiFi control in the Westinghouse or APUS models add convenience, while compact units like the Novieex or Ranein 3.6 GPM suit smaller spaces.
Consider your budget, installation requirements, and energy efficiency goals. All the reviewed models provide endless hot water and energy savings compared to traditional tanks. Choose one that fits your lifestyle, and enjoy the comfort of never running out of hot water again.
Erica Steven is the founder and lead writer of WorstBrands, a site dedicated to providing honest and trustworthy reviews about outdoor gear and fashion products.
With a passion for exploring the great outdoors and staying up to date on the latest fashion trends, Erica uses her expertise to provide valuable insights into the products that matter most to her readers.
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