Best Gas Water Heaters 40 Gallon

Peter | 23-12-2025

You will find our hand-picked selection of Best Gas Water Heaters 40 Gallon below. You have a wide variety of choices of brands such as Ranein,Rheem,VELPAX,thermomate,FOGATTI available to you as a result of the fact that each one of them has a unique pricing, look, and feel. Continue reading for an in-depth analysis in our Best Gas Water Heaters 40 Gallon buying guide!

Our experts tested a variety of Best Gas Water Heaters 40 Gallon on the market. Right at the top of the list is Ranein Best Gas Water Heaters 40 Gallon. Check out some more of our favorites below, and read some valuable insight from our experienced editors.

Editor's Choice
Ranein Natural Gas Tankless Water Heater with Vent Pipe, Indoor Max 4.3 GPM, 100,000 BTU Instant Hot
Ranein Natural Gas Tankless Water Heater with Vent Pipe, Indoor Max 4.3 GPM, 100,000 BTU Instant Hot
Premium Pick
Rheem 72-40-2 240V / 4500W 40 Gallon Electric Water Heater
Rheem 72-40-2 240V / 4500W 40 Gallon Electric Water Heater
Budget Pick
Natural Gas Tankless Water Heater,4.21GPM 16L Indoor,Instant Hot Gas water heater,Constant Natural
Natural Gas Tankless Water Heater,4.21GPM 16L Indoor,Instant Hot Gas water heater,Constant Natural

Top 10 Best Gas Water Heaters 40 Gallon

We researched and compared the top products in the Best Gas Water Heaters 40 Gallon category to provide you with these recommendations.

1. Ranein Natural Gas Tankless Water Heater with Vent Pipe, Indoor Max 4.3 GPM, 100,000 BTU Instant Hot

  • Performance: The on-demand tankless water heater boasts a heating capacity of 100,000 BTU and a hot water flow rate of 4.3 gallons per minute (GPM). It can provide continuous hot water for 2-3 water supply points, making it sufficient to meet the hot water needs of a household's bathroom, kitchen, and bar area.
  • Upgrade Features: Four Seasons Function: Automatically adjust the water temperature output based on the seasonal water temperature changes. Kitchen Function: Default water output temperature is 100F, suitable for kitchen use. Bathtub Function: Adjustable water output quantity with a reminder when the set output quantity is reached, catering to various environmental needs.
  • No Waiting Required: Unlike traditional tank water heaters, tankless water heaters eliminate the need for a 30-minute preheating wait time, allowing you to have unlimited hot water on demand.
  • Save Money: The kit already includes the exhaust pipe, so you don't need to spend extra money on purchasing it separately. With an oxygen-free copper water tank, it reduces heat loss and lowers energy consumption. Applied with standard 1/2" NPT water fitting and gas inlet.
  • Recommendation: We strongly advise that all installations of the device adhere to local building and plumbing regulations at the installation location, and should be carried out by licensed professionals. Not recommended for areas over 2,000 feet.

2. Rheem 72-40-2 240V / 4500W 40 Gallon Electric Water Heater

  • Rheemglas lined tank
  • R-Foam insulation
  • Anode Rod protects against corrosion
  • Automatic temperature control thermostat
  • Direct immersion heating element

3. Natural Gas Tankless Water Heater,4.21GPM 16L Indoor,Instant Hot Gas water heater,Constant Natural

  • Tankless Water Heater This natural gas tankless water heater features steady temperature control and multiple safety protections, including a flame failure device, anti-freeze protection, and overheating protection. It operates with just 3.6 PSI of water pressure, delivering up to 4.21 gallons of hot water per minute. With a maximum temperature rise of 65C(149F), this unit is designed exclusively for use with Natural GasLNG).
  • Efficient & Energy-Saving With a high-performance output of 68,000 BTU per hour, this 4.21 GPM instant natural gas water heater provides on-demand hot water for 23 points of use simultaneously, making it ideal for bathrooms and kitchens. The advanced combustion technology reduces operational noise for a more efficient and quieter experience.
  • Premium Quality & Durability Crafted with a stainless steel body for superior temperature and corrosion resistance, this natural gas water heater is built to last. The oxygen-free copper water tank ensures minimal heat loss and an extended service life. The LED smart digital display allows for easy temperature adjustments between 35C(95F) and 65C(149F), giving you precise control over your hot water needs.
  • Easy Installation & Use This tankless propane water heater is designed for quick and hassle-free setup. It comes equipped with standard 1/2" NPT water fittings,air inlet pipe, inlet and outlet water pipe, and a 2.5" horizontal vent pipe for easy installation.For safe operation, ensure proper ventilation and install a smoke exhaust pipe as required.
  • Versatile & Space-Saving This compact tankless water heater saves over 50% of space compared to traditional tank models, making it a perfect choice for homes, small cabins, and remote apartments. It efficiently meets both bathroom and kitchen hot water demands without the need for an expansion tank. Note: In cold weather, drain residual water by opening the pressure relief valve if the unit will not be used for an extended period.

4. ThermoMate CZ422NG Natural Gas Tankless Water Heater, Up to 5 GPM 113,000 BTU, High Efficiency

ThermoMate CZ422NG Natural Gas Tankless Water Heater, Up to 5 GPM 113,000 BTU, High Efficiency
8.9

Thermomate

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  • [Max 5 GPM & 113,000 BTU] - The ThermoMate instant hot water heater can supply two showers simultaneously, each delivering 105F water at a flow rate of 2 GPM, based on an inlet water temperature of 65F. No waiting time, no cold water shocks, perfect for busy households. Adopting advanced water flow sensor, the built-in chip can adjust the heating power 20,000 times per second, ensuring that the hot water within 1 fluctuations for a comfortable shower experience.
  • [Safety & Reliable] - This gas tankless water heater integrates 8 protections: boil-dry, freeze, flame-out, overheating, over-temperature, pipe blockage, high-temperature lock, and excessive air pressure. Equipped with 4 ceramic heating cores, it auto-activates frost protection when temperatures hit 41F (5). The energy-smart system uses minimal electricity to generate gentle warmth, preventing pipe ice buildup without high energy costs.
  • [Energy Efficient & Save Money] - The heat exchanger is constructed from high-quality oxygen-free copper, providing superior thermal conductivity and corrosion resistance compared to stainless steel. It achieves a thermal efficiency of 98% (vs. 80% for stainless steel models) and boasts a uniform energy factor (UEF) of 0.81. This design reduces energy waste, lowering annual operating costs by approximately 30% versus traditional systems.
  • [Smart Diagnostic Display] - Equipped with a 3.5-inch LED touchscreen, it allows you to effortlessly adjust and monitor output water temperature90F to 140Fwhile providing real-time tracking of water flow, fan operation, and flame status. Advanced error code technology enables rapid diagnosis of water heater malfunctions. The UL-certified 120V/5-foot power cord ensures continuous power supply for real-time monitoring systems.
  • [Easy to Install & Save space] - The whole house tankless water heater features standard 3/4" NPT water inlet/outlet connectors, a 1/2" NPT gas inlet, a 3" OD vent, and a UL-approved 120V plug, ensuring compatibility with most households. With its compact dimensions of 21"H x 13"W x 7"D, the on-demand water heater requires less than one-third of the space occupied by traditional tank models, freeing up valuable room in your home.
  • [Wind Resistant] - Engineered with a DC High-speed Fan (360Pa static pressure/3000 RPM), the system ensures powerful exhaust evacuation capable of withstanding winds from a major hurricane (Category 3 and above, >111 mph/178 km/h), eliminating safety risks like backdraft and flameouts during the most extreme weather.

5. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water Heater, 7.0 GPM,

  • High-efficiency tankless gas water heater delivers up to 7.0 GPM, perfect for 23 bathroom homes with multiple hot water needs like showers and laundry.
  • Powered by natural gas with 160,000 BTUs, this durable tankless unit ensures fast, reliable hot watereven during peak household demand.
  • Designed for outdoor installation, this high-efficiency tankless natural gas water heater features a durable metal cabinet and supports easy wall mounting by a qualified installer.
  • Hot-start programming prevents cold water bursts, making this tankless natural gas water heater ideal for back-to-back showers.
  • Rheem RTG tankless gas water heaters offer high-efficiency, space-saving designs with multiple models to fit any home size, fuel type, and hot water demand.

6. FOGATTI Natural Gas Tankless Water Heater Indoor - Max 7.5 GPM 170,000 BTU, CSA Certified Compact

FOGATTI Natural Gas Tankless Water Heater Indoor - Max 7.5 GPM 170,000 BTU, CSA Certified Compact
8.5

Fogatti

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  • Powerhouse Performance: The FOGATTI tankless water heater takes up a third of the space of traditional tank heaters but delivers 5 times the performance. With a high heating power of 170,000 BTU and a flow rate of 7.5 GPM, it provides endless hot water on demand, perfect for multitasking households
  • Instant Heating: Unlike traditional tank heaters, this tankless water heater gas delivers instant and endless hot water as water flows through. Whether its for showers, sinks, or appliances, even for 3-5 outlet points, it ensures uninterrupted hot water whenever you need it
  • Precision Temperature Control: With advanced water servo technology and temperature sensors, the gas tankless water heater indoor precisely adjusts water flow and gas intake to maintain a temperature difference within 1. The four-stage combustion system ensures consistent comfort, whether its a chilly winter or a hot summer
  • Quick and Easy Installation: The compact design measuring 25 x 16.3 x 7.3 inches makes installation hassle-free. Tankless gas water heater is compatible with low water pressure from 15-150 PSI, ensuring smooth operation even in areas with weaker water pressure. Simply connect to a standard 120V AC for seamless operation
  • Trusted Quality and Support: Built with a high-efficiency copper heat exchanger and 304 stainless steel burner, this water heater offers exceptional durability and performance. Certified by CSA and equipped with multiple safety features, it meets the highest safety standards for reliable operation
  • Reliable Protection and Support: The FOGATTI natural gas tankless water heater includes 2 years of full coverage for the entire unit and 5 years of coverage for the heat exchanger. Our dedicated customer support team is ready to assist with any questions or concerns, providing peace of mind for you
  • Note: Important Usage Guidelines: Tankless water heater natural gas is equipped with active heating anti-freeze device, If enviroment temp drop below 5 or not be used for long period, drain the water inside to prevent damage. For optimal performance, recommended for use below 2000 feet altitude

7. Ranein Propane Gas Tankless Water Heater with Vent Pipe, Indoor Max 4.3 GPM, 100,000 BTU Instant Hot

  • Performance: The on-demand tankless water heater boasts a heating capacity of 100,000 BTU and a hot water flow rate of 4.3 gallons per minute (GPM). It can provide continuous hot water for 2-3 water supply points, making it sufficient to meet the hot water needs of a household's bathroom, kitchen, and bar area.
  • Upgrade Features: Four Seasons Function: Automatically adjust the water temperature output based on the seasonal water temperature changes. Kitchen Function: Default water output temperature is 100F, suitable for kitchen use. Bathtub Function: Adjustable water output quantity with a reminder when the set output quantity is reached, catering to various environmental needs.
  • No Waiting Required: Unlike traditional tank water heaters, tankless water heaters eliminate the need for a 30-minute preheating wait time, allowing you to have unlimited hot water on demand.
  • Save Money: The kit already includes the exhaust pipe, so you don't need to spend extra money on purchasing it separately. With an oxygen-free copper water tank, it reduces heat loss and lowers energy consumption. Applied with standard 1/2" NPT water fitting and gas inlet.
  • Recommendation: We strongly advise that all installations of the device adhere to local building and plumbing regulations at the installation location, and should be carried out by licensed professionals. Not recommended for areas over 2,000 feet.

8. Natural Gas Tankless Water Heater,4.74GPM 18L Indoor,Instant Hot Gas water heater,Constant Natural

  • Tankless Water Heater This natural gas tankless water heater features steady temperature control and multiple safety protections, including a flame failure device, anti-freeze protection, and overheating protection. It operates with just 3.6 PSI of water pressure, delivering up to 4.74 gallons of hot water per minute. With a maximum temperature rise of 65C(149F), this unit is designed exclusively for use with Natural GasLNG).
  • Efficient & Energy-Saving With a high-performance output of 68,000 BTU per hour, this 4.74 GPM instant natural gas water heater provides on-demand hot water for 23 points of use simultaneously, making it ideal for bathrooms and kitchens. The advanced combustion technology minimizes gas consumption and reduces operational noise for a more efficient and quieter experience.
  • Premium Quality & Durability Crafted with a stainless steel body for superior temperature and corrosion resistance, this natural gas water heater is built to last. The oxygen-free copper water tank ensures minimal heat loss and an extended service life. The LED smart digital display allows for easy temperature adjustments between 35C(95F) and 65C(149F), giving you precise control over your hot water needs.
  • Easy Installation & Use This tankless natural gas water heater is designed for quick and hassle-free setup. It comes equipped with standard 1/2" NPT water fittings,gas pipe, inlet and outlet water pipe, and a 2.5" horizontal vent pipe for easy installation. For safe operation, ensure proper ventilation and install a smoke exhaust pipe as required.
  • Versatile & Space-Saving This compact tankless water heater saves over 50% of space compared to traditional tank models, making it a perfect choice for homes, small cabins, and remote apartments. It efficiently meets both bathroom and kitchen hot water demands without the need for an expansion tank. Note: In cold weather, drain residual water by opening the pressure relief valve if the unit will not be used for an extended period.

9. APUS Tankless Water Heater Propane Gas, Up to 4.42 GPM, Indoor Hot Water Heater, 95,000 BTU on

  • Powerful & High-Capacity: This high-performance propane tankless water heater delivers 95,000 BTU heating capacity with 4.42GPM high flow rate, featuring innovative 0.66GPM low-flow start technology. As a versatile propane tankless water heater, it meets simultaneous hot water demands for 2 showers plus 1 sink while maintaining stable temperatures even during peak usage.
  • Precise & Steady: With high-precision sensors and smart CPU technology, this tankless propane water heater maintains water temperature within 1F of your desired setting (adjustable from 95F-140F). No more sudden hot/cold shocksjust perfectly steady water for showers, washing, and more, even with multiple faucets running. Enjoy worry-free comfort every time!
  • Efficient & Durable: Featuring oxygen-free copper heat exchangers and innovative segmented combustion technology, this tankless water heater achieves exceptional 85%+ thermal efficiency. Designed for maximum performance, it delivers 30% greater energy savings than conventional tank water heater models.
  • Compact & Space-Saving: This compact propane water heater saves space without sacrificing performance, featuring an intuitive LED touchscreen and sleek dimensions of just 20.55"H 13.27"W 5.91"D. As a tankless propane water heater, it delivers instant hot water on demand while operating at a quiet 40dBquieter than most household appliances.
  • Safe & Reliable: Our reliable propane water heater includes multiple-layer safety protection and a 2-year coverage. This propane tankless water heater automatically shuts down if risks are detected, providing complete peace of mind with its instant, on-demand hot water comfort.

10. Ranein Natural Gas Tankless Water Heater, Indoor Max 3.6 GPM, 80,000 BTU Instant Hot Water Heater

  • Performance: The on-demand tankless water heater boasts a heating capacity of 80,000 BTU and a hot water flow rate of 3.6 gallons per minute (GPM). It can provide continuous hot water for 2-3 water supply points, making it sufficient to meet the hot water needs of a household's bathroom, kitchen, and bar area.
  • No Waiting Required: Unlike traditional tank water heaters, tankless water heaters eliminate the need for a 30-minute preheating wait time, allowing you to have unlimited hot water on demand.
  • Provides 4 modes: Dish mode(100), Fruit mode(95), Elderly mode(104) and Infant mode(107). More convenient for you to use.
  • Save Money: The kit already includes the exhaust pipe, so you don't need to spend extra money on purchasing it separately. With an oxygen-free copper water tank, it reduces heat loss and lowers energy consumption. Applied with standard 1/2" NPT water fitting and gas inlet.
  • Recommendation: We strongly advise that all installations of the device adhere to local building and plumbing regulations at the installation location, and should be carried out by licensed professionals.(Not recommended for areas over 2,000 feet)

Peter

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