10 Best Tankless Water Heaters 2026 in the United States

The Rheem 18kW 240V Tankless Electric Water Heater is a compelling option for those looking for an efficient, easy-to-install solution for their hot water needs. One of its standout features is the external digital thermostatic control with an LED display, which offers precise temperature control with +/- 1 degree accuracy. This makes it user-friendly and ensures you always get the perfect water temperature.

Its advanced self-modulation technology is another highlight, as it adjusts power usage based on your hot water demand, contributing to energy efficiency and potentially reducing your energy bills over time. The unit's flow rate is up to 4.4 gallons per minute (GPM), which should be sufficient for small to medium households but might not meet the demands of larger families with high simultaneous water usage.

The heater uses durable copper immersion heating elements that are field-serviceable, enhancing its longevity and ease of maintenance. Installation is straightforward with bottom 3/4 inch NPT water connections and threaded design, making it simple to replace existing water heaters. The compact size (14.5 inches wide and 18.25 inches high) allows it to fit in tight spaces, adding to its versatility. However, as an electric unit, it may not be as powerful as gas models in terms of temperature rise, especially in very cold climates.

The Rheem RTEX-24 24kW 240V Electric Tankless Water Heater offers a robust solution for continuous hot water supply with its impressive flow rate of up to 5.9 gallons per minute, making it suitable for households with moderate to high hot water demands. One of its standout features is the 99.8% energy efficiency, which helps in reducing energy costs and promoting eco-friendliness. The electric fuel type simplifies installation and maintenance compared to gas models, although it does require a 240V electrical connection, which some homes may need to upgrade to accommodate.

The compact dimensions (17.63”W x 18.25”H x 3.5”D) and wall-mount design make it space-efficient and ideal for small utility areas, while the digital temperature display and ON/OFF dial control provide ease of use and precise temperature adjustments. Additionally, the self-modulating power control enhances efficiency by only using the necessary amount of power based on the water flow rate.

However, the temperature rise might be limited during peak usage in colder climates, potentially requiring additional units for larger homes. Potential buyers should consider the installation requirements and whether their household electrical setup can support the unit. Those looking for a reliable, energy-efficient, and continuous hot water supply will find the Rheem RTEX-24 a compelling option, especially in moderate climates and homes with appropriate electrical infrastructure.

The Stiebel Eltron Tempra 29 Trend is a compact electric tankless water heater that provides continuous hot water on demand without running out, making it well suited for households wanting energy efficiency and space savings. Its sleek design fits well in tight spaces, and being electric, it doesn’t require venting, which simplifies installation in many homes. With a powerful 28.8 kW output and a temperature range up to 140°F, it can comfortably handle the hot water needs for a medium to large household, especially in warmer climates or for moderate flow rates around 3-4 gallons per minute.

The digital LED display allows easy temperature adjustments, and its silent operation adds to user comfort. However, it requires a minimum 200-amp electrical service, which may mean upgrading home wiring if your system is older or lower capacity. The unit’s water capacity is very small (0.39 gallons), typical for tankless models, so it heats water instantly but demands stable electrical supply. Maintenance is generally low but periodic descaling may be needed depending on water hardness. The included 7-year leakage and 3-year parts warranties provide solid peace of mind.

This model suits those who want a reliable, energy-saving electric tankless heater with easy installation in homes prepared for its electrical requirements.