10 Best Tankless Instant Water Heaters 2025 in the United States

The Rinnai RXP199iN Condensing Smart Sense Tankless Water Heater is a versatile option that can be installed indoors or outdoors. The ability to use either natural gas or propane makes it adaptable for different homes. With a flow rate of up to 11.1 gallons per minute, it can comfortably serve multiple fixtures simultaneously, ensuring you never run out of hot water. Its high energy efficiency factor of UEF .98 is commendable, meaning it uses energy very effectively and could help reduce utility bills over time.

The Smart-Circ Intelligent Recirculation feature is a notable advantage as it learns your usage patterns to optimize hot water availability and efficiency. Additionally, its compact size (19”W x 31”H) helps save space, making it an excellent choice for smaller homes or apartments. Professional installation is strongly recommended, which can add to the upfront cost. While it has a modern design and the potential for WiFi connectivity via the Control-R module, this add-on is not included and must be purchased separately.

The 199,000 BTU heat output ensures a significant temperature rise, capable of handling high-demand scenarios. Warranty and support are accessible through Rinnai’s website.

The Stiebel Eltron Tempra 29 Trend tankless water heater is a robust and efficient option for those needing continuous hot water. With a 28.8kW power output, it ensures a consistent flow of hot water, making it suitable for whole-house use. The unit boasts strong energy efficiency, thanks to its auto-modulation feature, which adjusts the energy consumption based on demand.

Its compact design saves space and does not require venting, making installation simpler and more versatile. Additionally, the silent operation and easy-to-read digital temperature display add to its user-friendly experience. The solid copper heating system ensures durability and reliability. However, it requires a significant electrical service (200 A), which may necessitate electrical upgrades for some homes.

The warranties provided (7 years for leakage and 3 years for parts) offer added peace of mind. Even though there might be an initial investment and potential need for electrical upgrades, the Tempra 29 Trend is a worthy choice for households seeking efficient, eco-friendly, and reliable hot water on demand.

The Rinnai V53DeP Propane Tankless Water Heater is designed to provide endless hot water with a flow rate of 5.3 gallons per minute, which should be adequate for small to medium-sized households with moderate hot water demands. Its energy-efficient propane fuel system heats water on demand, reducing wasted energy and potentially lowering utility bills. One of the standout features is its compact design, ideal for outdoor installations where space might be limited. However, since it is an outdoor unit, it might not be suited for areas with extreme weather conditions without additional protection.

The heater includes enhanced scale detection to help maintain its efficiency and prolong its lifespan. It also offers Wi-Fi capability, allowing for convenient remote management and monitoring. For installation, professional assistance is recommended to ensure safety and optimal functioning, which could mean additional upfront costs if not already considered.

The product is backed by a robust warranty, including a 10-year warranty on the heat exchanger, which reflects confidence in its durability. Customer reviews are generally positive, highlighting reliability and performance, though some users may note the initial complexity of setup and installation as a drawback.

This Rinnai model is ideal for those looking for a high-efficiency, space-saving water heating solution with modern features like Wi-Fi connectivity. However, it may not be the best choice for users in very cold climates unless additional measures are taken to protect the unit from freezing. It stands out for its combination of efficiency, advanced features, and compact design, making it a strong contender in the tankless water heater market.