10 Best Tankless Hot Water Heaters 2026 in the United States

The Rinnai RXP199iN is a versatile tankless water heater designed for both indoor and outdoor use, thanks to its Versa Vent system. It runs on either natural gas or propane, which adds flexibility depending on your fuel preference. With a strong flow rate of up to 11.1 gallons per minute, it can supply hot water to around seven fixtures simultaneously, making it suitable for medium to large households. Its energy efficiency is excellent, boasting a UEF (Uniform Energy Factor) of 0.98, which means it uses fuel very efficiently and can help reduce energy bills.

The Rinnai RE199iN is a natural gas tankless water heater designed for indoor use, offering a strong flow rate of up to 9.8 gallons per minute (GPM). This means it can handle multiple fixtures at once, making it suitable for larger households or homes with higher hot water demand. It operates efficiently by heating water only when needed, which can help reduce energy waste compared to traditional tank heaters. The unit has a powerful 199,000 BTU output, supporting a good temperature rise for most household needs, with a maximum temperature of 140°F. Its compact size (about the size of a small suitcase) allows for easier installation on a wall, saving space in your home. However, professional installation is recommended due to the gas connection and complexity, which is common for gas-powered tankless heaters. The product includes a solid warranty: 15 years on the heat exchanger, 5 years on labor, and 1 year on parts, giving confidence in its durability.

The Rinnai RE180iP tankless water heater is a solid choice if you want a propane model that delivers hot water consistently without taking up much space. It can supply up to 8.5 gallons per minute, which means it can handle multiple fixtures running at once—great for medium to large households. Being propane-fueled, it’s efficient and powerful with a 180,000 BTU rating, but since it’s a non-condensing model, it isn’t as energy-efficient as condensing units. However, its smart design helps conserve energy by heating water only when needed.