10 Best Indoor Gas Tankless Water Heater 2025 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 RX130iN tankless water heater is a solid choice if you want a compact, efficient solution for your hot water needs. It delivers up to 7.1 gallons per minute, which is enough to supply hot water to about four fixtures at once—great for medium-sized homes. Its energy efficiency is excellent, with a UEF rating of 0.97, meaning it uses gas very efficiently and can help reduce energy bills compared to traditional water heaters. The 130,000 BTU rating provides strong heating power, so it can quickly heat water even in colder climates.

One standout feature is its versatile installation options: it can be mounted indoors or outdoors thanks to the Versa Vent system, and it works with both natural gas and propane via its Smart Sense gas control. This flexibility is handy if your home setup or space is limited. The unit itself is fairly compact (about the size of a small suitcase) and wall-mounted, which saves floor space.

Installation is not a DIY job; Rinnai recommends professional installation to ensure safety and optimal performance. While the unit has smart features like WiFi control (with an optional module) and an easy interface, these add-ons are extra and not included out of the box. The unit weighs 54 pounds, so it's relatively easy to handle during installation. It comes with a warranty, and Rinnai offers good customer support with manuals, guides, and an app for setup and troubleshooting. If you’re looking for a reliable, energy-efficient tankless water heater that adapts to different fuel types and installation locations, the Rinnai RX130iN is a fitting option. Just be prepared to hire a professional for installation and possibly invest in extra smart control modules if you want remote access.

The Rinnai RX180iN is a powerful and versatile indoor gas tankless water heater that can run on natural gas or propane. It delivers up to 10 gallons per minute, which means it can supply hot water to about six fixtures at the same time — a solid choice for medium to large homes. With a high BTU rating of 180,000, it quickly heats water to your desired temperature without delay. Its energy factor of 0.98 means it’s very efficient, helping to reduce your utility bills compared to older models.

The unit is fairly compact, about the size of a small suitcase, making it easier to fit in tight spaces. It also has flexible venting options and can be installed indoors or outdoors with the proper vent cap, adding to installation convenience. The interface is user-friendly, and it supports smart features like WiFi control through an optional module, allowing you to monitor and adjust settings remotely. However, this model is designed to be professionally installed, so DIY installation is not recommended. One thing to keep in mind is the 140°F maximum temperature, which is sufficient for most households but might be limiting if you need hotter water.

This Rinnai model represents a reliable, energy-efficient tankless heater with good flow capacity for everyday use, making it an excellent choice for those who appreciate modern features and flexible installation.