10 Best Indoor Gas Tankless Water Heater 2025 in the United States

The Ranein Natural Gas Tankless Water Heater is designed for indoor use and offers a substantial flow rate of up to 7.4 GPM, making it suitable for medium to large households with 4-6 outlets. With a high heating capacity of 190,000 BTU, this unit ensures instant and continuous hot water without the need for preheating, which is a significant advantage over traditional tank heaters. The fans placed underneath enhance safety by preventing smoke backflow and ensuring full combustion with low noise levels and longer service life.

Its compact design (24.25”L x 15.08”W x 8.07”H) allows for easy installation in smaller spaces, and it uses standard fittings for convenience. Additionally, the product comes with a 2-year warranty, providing some peace of mind, although this is relatively short compared to some competitors who offer longer warranties. However, there are a few drawbacks. The unit is not recommended for use in areas above 2,000 feet altitude, which could limit its applicability.

Moreover, users in colder climates need to manually drain the unit if it's not used for a while to prevent damage, adding a bit of maintenance. Despite these minor issues, the Ranein Natural Gas Tankless Water Heater is a strong contender for households needing an efficient and reliable hot water solution.

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 Ranein Natural Gas Tankless Water Heater offers a solid performance with a heating capacity of 100,000 BTU and a maximum flow rate of 4.3 gallons per minute (GPM). This makes it suitable for providing continuous hot water to multiple points in a household, such as a bathroom, kitchen, and bar area. One of the standout features is the Four Seasons Function, which automatically adjusts the water temperature based on seasonal changes, and the Kitchen Function, which sets the default temperature to 100°F for kitchen use.

Additionally, the Bathtub Function allows for adjustable water output with reminders, enhancing convenience for various needs. Immediate hot water on demand eliminates the need for preheating, a significant advantage over traditional tank water heaters. The inclusion of the exhaust pipe in the kit saves additional costs and simplifies installation. The energy efficiency is bolstered by the oxygen-free copper water tank, which reduces heat loss and lowers energy consumption.

However, it's essential to adhere to local building and plumbing regulations and opt for professional installation. A notable limitation is that it is not recommended for use at elevations over 2,000 feet, which might restrict its applicability in high-altitude areas. The compact design, with dimensions of 18.89 inches in width and 8.85 inches in height, makes it suitable for homes with limited installation space. This tankless water heater is ideal for households needing efficient and continuous hot water but may not be suitable for high-altitude regions.