10 Best On Demand Water Heaters 2025 in the United States

The Rinnai RXP199iN Condensing Smart Sense Tankless Water Heater stands out with its impressive flow rate of up to 11.1 gallons per minute (GPM), which can support multiple fixtures simultaneously. This makes it a great choice for larger households or those with high hot water demand. The energy efficiency is excellent, boasting a Uniform Energy Factor (UEF) of 0.98, meaning it effectively converts fuel into usable heat, leading to potential savings on energy bills.

The device operates on both natural gas and propane, offering flexibility depending on your fuel availability or preference. Its compact size, similar to a small suitcase, allows for versatile installation either indoors or outdoors, thanks to the Versa Vent system. Additionally, the Smart-Circ Intelligent Recirculation feature learns your hot water usage patterns to optimize performance and efficiency, though it may take some time to adjust correctly to your routine.

The unit is fairly lightweight at 58 pounds, but professional installation is strongly recommended to ensure proper setup and operation. A potential downside is the additional cost for the Control-R module if you want WiFi connectivity for remote control and monitoring. Also, while the temperature rise and maximum output of 199,000 BTU are suitable for most homes, it's important to ensure it's compatible with your specific requirements. This water heater is highly efficient and powerful, suitable for households needing a reliable and flexible hot water solution.

The Rinnai RX199iN is a versatile tankless water heater suitable for both indoor and outdoor use, powered by natural gas or propane. It delivers a strong flow rate of up to 11.1 gallons per minute, which means it can supply hot water to about seven fixtures at once, making it a good choice for larger households or homes with high hot water demand. Its energy efficiency is impressive, with a UEF of 0.98, indicating that it uses fuel very effectively, which can lower your energy bills over time. The heater is compact, roughly the size of a small suitcase, and mounts on the wall, saving space compared to traditional tank water heaters.

It offers a maximum temperature of 140°F and a powerful 199,000 BTU output, ensuring a consistent temperature rise even in colder climates. This model requires professional installation, which adds to the upfront cost and complexity. The smart control system and available WiFi module allow convenient temperature adjustments and maintenance alerts, enhancing user experience. Warranty and support appear reliable, and Rinnai provides resources like manuals and installation help.

On the downside, it’s relatively heavy at 55 pounds, and you’ll need to ensure the proper venting system (Versa Vent and vent cap for outdoors) is in place. If you want a high-capacity, energy-efficient tankless water heater with modern features and don’t mind investing in professional installation, the Rinnai RX199iN represents a solid option.