10 Best Tankless Hot Water Heaters 2025 in the United States

The Rinnai RX199iN is a powerful tankless water heater that stands out for its impressive flow rate of up to 11.1 gallons per minute, making it suitable for homes with multiple fixtures needing hot water simultaneously. It's designed to operate on either natural gas or propane, giving you flexibility depending on your fuel source. The energy efficiency is top-notch, boasting a UEF rating of .98, which means it uses energy very effectively, potentially saving you on utility bills.

One of the great features is its compact size, comparable to that of a small suitcase, making it easier to fit into various spaces. The Smart Sense gas control system adds convenience, allowing for easier operation. However, the installation of this unit is recommended to be done by a professional. While this ensures safety and proper functionality, it could increase your expenses if you don’t have a technician readily available.

While its high efficiency is a significant advantage, it may not be the best choice for all water temperature needs depending on your region’s groundwater temperature. Additional considerations include the need for the RX-OVC vent cap for outdoor installation, which adds to the installation complexity and cost. Also, the Controlr module for WiFi control is sold separately, which might be a drawback for those looking for smart home integration right out of the box. If you are looking for a tankless heater that offers high performance and efficiency, the Rinnai RX199iN is a strong contender. Just ensure you’re prepared to handle the installation requirements and additional features you may want to consider.

The Rheem 18kW 240V Tankless Electric Water Heater in Gray offers several appealing features for those in need of a compact and efficient water heating solution. The primary advantages of this model include its advanced self-modulation technology, which helps adjust power based on the hot water demand, ensuring energy efficiency and cost savings. Additionally, it boasts a flow rate of up to 4.4 GPM, which is suitable for small to medium households, providing enough hot water for multiple uses simultaneously.

The external digital thermostatic control with an LED display allows for precise temperature adjustments, enhancing user convenience and comfort. The heater is also equipped with durable copper immersion heating elements, which are field serviceable, making it easier to maintain and extend its lifespan. Installation is straightforward due to the bottom 3/4 inch NPT water connections and threaded design, allowing for easy replacement if necessary.

However, there are some drawbacks to consider. As an electric heater, it may not be as efficient or cost-effective in areas with high electricity rates compared to gas-powered models. Additionally, the temperature rise might be limited in very cold climates, potentially affecting the heater's performance. The size and installation process, while simple, may still require professional assistance for those unfamiliar with electrical systems. Lastly, it's essential to review the warranty and support options from Rheem to ensure long-term reliability. The Rheem 18kW 240V Tankless Electric Water Heater is a strong choice for individuals seeking an energy-efficient, easy-to-use, and maintain water heating solution within the limitations of an electric-powered system.

The Rinnai RL75IN Tankless Hot Water Heater offers a robust performance with a flow rate of 7.5 gallons per minute (GPM), making it capable of supplying hot water to up to 5 fixtures simultaneously. This is particularly advantageous for families or homes with multiple bathrooms. The unit uses natural gas, which can be more cost-effective compared to electric models, and it is designed for indoor installation, saving outdoor space and making it suitable for various home layouts.

The compact size is another plus, as it can fit into smaller spaces without sacrificing performance. A notable feature is its Circ-Logic technology, which allows users to set recirculation patterns based on their hot water usage habits, potentially leading to reduced water and energy wastage. However, the unit is non-condensing, meaning it may not be as energy-efficient as condensing models, which could lead to higher operational costs over time.

The product includes a solid warranty, with up to 12 years on the heat exchanger for residential use, but it is recommended to have it professionally installed, which could add to the initial cost. Additionally, while it offers WiFi control, the necessary module is not included and must be purchased separately. This heater is best suited for mid to large-sized homes that require reliable and continuous hot water supply, but it may not be the best choice for those looking for the highest energy efficiency or those on a tight budget due to the additional installation and WiFi module costs.