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

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 RX160iN Condensing Smart Sense Tankless Water Heater is a versatile option for those looking to upgrade their home water heating system. It can be installed indoors or outdoors and works with either natural gas or propane, thanks to its Smart Sense gas control system. With a capacity of up to 9 GPM, it is capable of supplying hot water to up to six fixtures simultaneously, making it suitable for medium to large households.

Its compact size (19"W x 31"H) is a space-saver, and it weighs just 54 pounds, which helps with easier installation, although professional setup is recommended for optimal performance and safety. The unit boasts a high energy efficiency rating (UEF .97), meaning it can help reduce energy costs over time. Additionally, features like the Quick Flush system make maintenance simpler, and optional WiFi connectivity (via the Controlr module, not included) allows for remote control and monitoring of the system.

The need for an additional vent cap (RX-OVC) for outdoor installations could be seen as an extra cost, and the professional installation requirement might be a drawback for some. It also has a maximum BTU rating of 160,000, ensuring robust performance. Warranty and detailed product guides from the manufacturer provide added peace of mind. The Rinnai RX160iN represents a reliable and efficient choice for those seeking a high-performance tankless water heater, particularly in regions where the ground water temperature is compatible.

The Rinnai RE199iN is a solid option for those looking for a reliable indoor gas tankless water heater. It delivers a strong flow rate of up to 9.8 gallons per minute, which means it can supply hot water to multiple fixtures at once without running out quickly—great for larger households. Its high BTU rating of 199,000 indicates it has powerful heating capacity to quickly warm water even in colder climates. Although it’s a non-condensing model, which typically means slightly lower energy efficiency compared to condensing heaters, it still features an improved design that heats water only when needed, helping save energy.

The compact size, roughly the size of a small suitcase, makes it easier to fit into tight indoor spaces. Installation should be handled by a professional due to venting and safety requirements, and Rinnai supports the product with a strong warranty—15 years on the heat exchanger, which is a key component, plus coverage for labor and parts. The LED display adds user-friendly service reminders and error codes to help with maintenance.

One thing to note is the absence of a built-in recirculation pump, which means you might have to purchase an additional model if you want quicker hot water delivery at fixtures. This unit suits homeowners who want dependable, continuous hot water with a focus on durability and manageable energy use, but don’t necessarily need the highest efficiency or extra smart features built-in.