Best Gas Tankless Water Heater for Large Homes [In 2025]

Homeowners seeking an efficient and reliable hot water solution for their large homes often turn to gas tankless water heaters. These on-demand systems provide a continuous supply of hot water, saving space and reducing energy costs compared to traditional tank-style heaters. In this comprehensive review, we’ll explore three top-performing gas tankless water heater options to help you find the best fit for your household.

Tankless water heaters have gained popularity in recent years due to their energy-efficient performance and space-saving design. Unlike conventional tank heaters, tankless models heat water only when it’s needed, eliminating standby energy losses and providing a continuous flow of hot water. This makes them an excellent choice for larger homes with high hot water demands.

The products we’ll be reviewing are:

1. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater
2. FOGATTI Natural Gas Tankless Water Heater – Outdoor Installation
3. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Heater
4. Rinnai RE140iN Non-Condensing Natural Gas Tankless Water Heater

Each of these gas tankless water heaters offers unique features and specifications to meet the needs of different household sizes and configurations. Let’s dive in and explore the details of each model.

5 Best Gas Tankless Water Heater for Large Homes Review

NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater

Specs:

• Fuel Type: Natural Gas or Propane
• BTU Input: 199,000
• Flow Rate: Up to 11.1 GPM
• Energy Factor (UEF): 0.98
• Dimensions: 18.5 x 9.3 x 14 inches
• Weight: 58 lbs

Pros:

• Convertible fuel source (natural gas or propane)
• Highly efficient condensing technology (0.98 UEF)
• Impressive flow rate of up to 11.1 GPM
• Compact, space-saving design
• Versatile installation (indoor or outdoor)
• Smart Sense gas control system

Cons:

• Professional installation is recommended
• Wi-Fi connectivity requires separate Control-R module

FOGATTI Natural Gas Tankless Water Heater – Outdoor Installation

Specs:

• Fuel Type: Natural Gas
• BTU Input: 180,000
• Flow Rate: Up to 8.1 GPM
• Dimensions: 26.2 x 17.1 x 7.1 inches
• Weight: 58.4 lbs

Pros:

• Designed for outdoor installation
• Precise temperature control within ±1°F
• Compact and easy to install
• Durable stainless steel construction
• Includes 2-year full coverage and 5-year heat exchanger warranty

Cons:

• Not suitable for use in very cold climates below 5°F
• May not be suitable for homes with extremely low water pressure

Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Heater

Specs:

• Fuel Type: Natural Gas
• BTU Input: 70,000
• Flow Rate: Up to 7.0 GPM
• Energy Factor (EF): 0.82
• Dimensions: 14 x 10 x 6 inches
• Weight: 33 lbs

Pros:

• High-efficiency non-condensing technology
• Compact, wall-mounted design saves space
• Includes leak detection and prevention features
• Hot-start programming avoids cold water bursts
• Suitable for small to medium-sized homes

Cons:

• Lower flow rate compared to larger models
• May not be suitable for homes with high hot water demand

Rinnai RE140iN Non-Condensing Natural Gas Tankless Water Heater

Specs:

• Fuel Type: Natural Gas
• BTU Input: 140,000
• Flow Rate: Up to 5.3 GPM
• Dimensions: 18.5 x 9.3 x 14 inches
• Weight: 46 lbs

Pros:

• Compact, space-saving design
• Durable construction with long-lasting components
• Includes 15-year heat exchanger warranty
• Can be made “smart” with Rinnai Controlr module

Cons:

• Lower flow rate compared to larger models
• Professional installation is recommended

Buying Guide: Choosing the Best Gas Tankless Water Heater for Large Homes

When selecting a gas tankless water heater for a large home, there are several key factors to consider:

Flow Rate

• Look for a model with a high flow rate (ideally 8 GPM or more) to meet the hot water demands of a large household.
• Consider the number of bathrooms, appliances, and simultaneous usage in your home to determine the appropriate flow rate.

BTU Input

• Higher BTU inputs (typically 140,000 BTU or more) provide more heating power to deliver hot water efficiently.
• Match the BTU rating to the size of your home and hot water needs.

Energy Efficiency

• Opt for a model with a high energy factor (EF or UEF) to maximize energy savings and reduce utility costs.
• Condensing tankless heaters tend to be the most energy-efficient, but non-condensing models can also be highly efficient.

Installation Considerations

• Determine if you need an indoor or outdoor model based on your home’s layout and local climate.
• Ensure the tankless heater is compatible with your home’s gas supply and plumbing system.
• Professional installation is highly recommended for safety and optimal performance.

Warranty and Support

• Look for a tankless water heater with a comprehensive warranty, including coverage for the heat exchanger and other key components.
• Choose a reputable brand that offers reliable customer support and a network of authorized service providers.

FAQs

How do gas tankless water heaters differ from traditional tank-style heaters?

Gas tankless water heaters heat water on demand, rather than storing a limited volume of hot water like a traditional tank heater. This on-demand heating saves energy by eliminating standby losses and provides an endless supply of hot water.

What is the typical lifespan of a gas tankless water heater?

With proper maintenance, gas tankless water heaters can last 20 years or more, significantly longer than the 10-15 year lifespan of a traditional tank heater.

Do gas tankless water heaters require special venting?

Yes, gas tankless water heaters typically require dedicated venting, either through a direct vent system or a power vent. This ensures proper exhaust of combustion gases.

Conclusion

Choosing the best gas tankless water heater for a large home requires careful consideration of factors like flow rate, BTU input, energy efficiency, and installation requirements. The four models reviewed in this article – the Rinnai RX199iN, FOGATTI Natural Gas Tankless, Rheem RTG-70DVLN-3, and Rinnai RE140iN – each offer unique features and specifications to suit different household needs. By understanding your hot water demands and weighing the pros and cons of each option, you can select the gas tankless water heater that will provide reliable, efficient, and endless hot water for your family.