10 Best high efficiency tankless electric hot water heaters 2026 in the United States

The Rheem RTEX-24 24kW 240V Electric Tankless Water Heater offers an impressive flow rate of up to 5.9 gallons per minute (GPM), which is quite strong for most household needs. Its self-modulating power control ensures efficient energy use by adjusting power based on hot water demand, contributing to its notable 99.8% energy efficiency.

The adjustable digital temperature display with an ON/OFF dial control makes it user-friendly, allowing for precise temperature adjustments and easy monitoring. Installation should be straightforward with its compact size (17.63”W x 18.25”H x 3.5”D) and wall-mount design, although professional installation is recommended due to the 24kW power requirement and 240V voltage. The unit's weight of 17.8 pounds is manageable for most installation scenarios.

Durability is supported by the stainless steel finish and robust build. The maximum water pressure of 150 PSI should be checked against your home’s water pressure to ensure compatibility. This heater is well-suited for homeowners looking for an efficient, high-performing solution to provide continuous hot water on demand.

The Rheem 18kW 240V Tankless Electric Water Heater is a high-efficiency water heating solution with several notable strengths. Featuring an external digital thermostatic control with an LED display, it allows precise temperature management with a +/- 1 degree accuracy. This level of control is beneficial for maintaining consistent water temperature. The self-modulation feature is another significant advantage, as it adjusts power usage based on hot water demand, enhancing energy efficiency and potentially lowering electricity costs.

With a flow rate of up to 4.4 gallons per minute (GPM), it can support multiple fixtures simultaneously, making it ideal for medium-sized households. The durable copper immersion heating elements are robust and field-serviceable, ensuring longevity and ease of maintenance. Additionally, the unit's design includes bottom 3/4 inch NPT water connections and threaded connections, simplifying installation and replacement processes.

However, the product does have some limitations. The power requirement of 18,000 watts at 240 volts may be high for some homes, necessitating a professional electrical assessment before installation. Additionally, the product dimensions, while relatively compact, might still require adequate space for installation. The Rheem 18kW 240V model stands out as an efficient and reliable option for those seeking a tankless electric water heater with modern features and strong performance.

The Stiebel Eltron Tempra 36 Plus is a high-powered tankless electric water heater designed to deliver continuous hot water on demand. It operates at 27,000 watts with a maximum flow rate of 1.5 gallons per minute, which is suitable for smaller households or point-of-use setups but might be limiting if you need simultaneous hot water at multiple fixtures. Its advanced flow control and self-modulation technology help save energy by adjusting power use based on demand, making it a strong choice if you're looking to reduce utility bills.

The digital LED display allows for precise temperature control, which adds convenience and helps maintain consistent water temperature. Installation is straightforward with a floor mounting method, and the unit is relatively compact at about 17 by 14.5 inches, so it won’t take up much space. However, it requires a 208-volt power supply, which might need electrical upgrades in some homes. The product is well-reviewed for reliability and efficiency.

If you want an energy-efficient electric tankless heater for a smaller capacity setting and don’t mind the electrical requirements, the Tempra 36 Plus represents a solid, dependable option.