10 Best Tankless Hot Water Heaters 2026 in the United States

The Rheem RTEX-24 Electric Tankless Water Heater is a solid choice for those seeking an efficient and high-capacity water heating solution. One of its major strengths is its impressive flow rate of up to 5.9 gallons per minute (GPM), which is suitable for serving multiple fixtures simultaneously. Additionally, its 99.8% energy efficiency rating makes it an economical option, as it minimizes energy waste and reduces utility bills.

The electric fuel type ensures ease of installation without the need for gas lines, making it a convenient option for many users. Its compact size (17.63"W x 18.25"H x 3.5"D) and wall-mount capability further enhance its suitability for smaller spaces or areas where floor space is at a premium. The product also boasts a user-friendly digital temperature display and self-modulating power control, which contribute to maintaining consistent and continuous hot water supply on demand.

However, there are some drawbacks to consider. The maximum flow rate may not be sufficient for larger households with high hot water demands during peak usage times. In summary, the Rheem RTEX-24 is an excellent option for small to medium-sized households or professional use, offering high efficiency, ease of installation, and reliable performance within its capacity limits.

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 RE140iP is a propane-fueled tankless water heater designed for indoor use that delivers up to 5.3 gallons per minute (GPM), which means it can supply hot water to about five fixtures at the same time. This flow rate generally fits medium-sized homes or households with moderate simultaneous hot water needs. It uses 140,000 BTU of power, which is strong enough to provide a good temperature rise even if your incoming water is cold, making it suitable for most climates when properly sized.

The unit is compact, roughly the size of a small suitcase, and wall-mountable, helping save space compared to traditional tank heaters. Its design includes an LED display that shows service reminders and error codes, which can make maintenance easier. Energy efficiency is marked as high, partly due to the heater only activating when hot water is needed, helping keep utility bills lower. The product requires professional installation, which is common for gas heaters to ensure safety and compliance with local codes.

Warranty coverage is solid, offering 15 years on the heat exchanger, 5 years on labor, and 1 year on parts, giving peace of mind for the long term. This model is non-condensing, which typically means it wastes more energy compared to condensing models, so while it's efficient, it may not be the absolute best in fuel savings. Also, it’s designed for indoor use only, so installation options are somewhat limited. If you’re comfortable with propane and need a reliable, space-saving water heater with good flow and durability, this Rinnai model fits well. However, if maximum energy savings or outdoor installation flexibility are top priorities, you might want to explore other options.