10 Best Indoor Gas Tankless Water Heater 2026 in the United States

The Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Tankless Water Heater is a strong contender for anyone looking to upgrade their home’s hot water system. With a flow rate of up to 11.1 gallons per minute (GPM), it can easily handle multiple fixtures simultaneously, making it suitable for larger households or those with high hot water demands. Its high BTU rating of 199,000 ensures quick heating, which is a significant advantage over traditional tank water heaters.

Energy efficiency is another highlight, boasting a UEF rating of .98, which means it consumes less energy compared to many alternatives. This not only translates to lower utility bills but also aligns well with environmentally conscious choices. The compact design, about the size of a small suitcase, allows for flexible installation in various spaces, whether indoors or outdoors, thanks to the Versa Vent feature.

However, there are some drawbacks to consider. The requirement for professional installation may add to the cost, particularly for those who are looking to save on installation fees by doing it themselves. Additionally, while the Smart Sense gas control system simplifies usage and efficiency, it doesn’t come with the compatible WiFi module by default, which may be a missed feature for tech-savvy users seeking remote management.

The Rinnai RXP199iN Condensing Smart Sense Tankless Water Heater is a solid choice for those looking for an efficient indoor gas water heater. With a flow rate of up to 11.1 gallons per minute (GPM), it can easily supply hot water to several fixtures simultaneously, making it ideal for larger households. Its high BTU rating of 199,000 means it can heat water quickly, ensuring you never run out of hot water when you need it most.

One of the standout features of this model is its impressive energy efficiency, with a UEF rating of .98. This means it can help you save on energy bills over time, which is a significant advantage for environmentally conscious consumers. The Smart-Circ technology is another highlight; it learns your hot water usage patterns to optimize recirculation, ensuring you get hot water faster without wasting energy.

There are some things to keep in mind. The installation process is recommended to be done by a professional, which could add to your overall costs if you're planning to buy this unit. Its compact size is a plus, but you'll still need adequate wall space for installation. Additionally, while it supports WiFi connectivity through the Control-R module, this feature is sold separately, which could be an extra expense for those looking for smart home integration.

The Rinnai RXP160iN tankless water heater is a versatile choice for those needing a reliable indoor gas water heater that can also be installed outdoors with the proper venting accessories. It delivers a strong flow rate of up to 9 gallons per minute, making it suitable for multiple fixtures running at the same time in a typical household. The heater boasts a high energy efficiency rating of 0.97, which means it uses fuel very effectively, helping to reduce energy bills. Its powerful 160,000 BTU output means it can rapidly heat water even during heavy use.

The unit includes a Smart-Circ recirculation pump that learns your usage patterns to provide hot water quickly when needed, cutting down on wait times and wasted water. With dimensions of 19 by 31 inches, it’s compact enough to fit in tight spaces but still requires professional installation due to its complexity and venting needs. While it supports both natural gas and propane, ensuring flexibility based on your home’s fuel source, outdoor installation requires an additional vent cap.

The smart features, including WiFi compatibility via an optional module, make it modern and convenient for users who want to monitor or adjust settings remotely. The unit’s warranty and support through Rinnai’s professional installers offer peace of mind. The main drawbacks are the need for professional installation, which adds to upfront costs, and the requirement of specific venting accessories for outdoor use. This model is ideal for homeowners seeking a high-efficiency, compact, and smart tankless water heater that efficiently handles multiple fixtures.