10 Best Electric Tankless Water Heaters 2026 in the United States

The Rheem 18kW 240V Tankless Electric Water Heater is a solid choice for those looking for an efficient and reliable source of hot water. With a maximum flow rate of up to 4.4 gallons per minute (GPM), it can meet the demands of small to medium households effectively. One of its standout features is the external digital thermostatic control with a precise +/- 1 degree accuracy, allowing users to easily set and maintain their desired water temperature.

Energy efficiency is another strong point, boasting an impressive 99.8% efficiency rating, which can help reduce electricity bills over time. The self-modulation technology adjusts power based on hot water demand, ensuring energy is used only when needed. Additionally, it is compact in size, making it suitable for installations in tighter spaces.

Installation is made easy with the bottom 3/4 inch NPT water connections and threaded fittings, which simplify the process for homeowners and professionals alike. However, it’s important to note that this model is designed for wall mounting, which may require additional considerations for some users. Some users may find that the 18kW power rating is not sufficient for larger households with multiple simultaneous hot water needs. While it serves well for typical use, those with higher demand might need to consider a more powerful unit. Additionally, it may require professional installation, which can add to the overall cost.

The Rheem RTEX-24 24kW 240V Electric Tankless Water Heater offers solid performance for households looking for a reliable source of on-demand hot water. One of its strong points is the flow rate, with the capacity to deliver up to 5.9 gallons per minute, which should be sufficient for multiple outlets running simultaneously. The unit's self-modulating power control and adjustable digital temperature display are user-friendly features that allow for precise temperature adjustments and energy savings, contributing to its high energy efficiency rating of 99.8%. This makes it an economical choice in the long run.

Additionally, the unit is compact, with dimensions of 17.63 inches wide and 18.25 inches high, making it easier to install in various spaces. It is designed for wall mounting, which can save floor space in tight utility areas. However, the power requirements are quite high at 24kW and 240V, which means it might require an upgrade to your electrical system if your current setup isn't compatible. This could add to the installation cost and complexity.

The unit also comes with necessary fittings and aerators, which is a plus. In conclusion, the Rheem RTEX-24 is an efficient and high-capacity option suitable for those who need consistent hot water and have the necessary power infrastructure.

The Stiebel Eltron Tempra 36 Trend is a powerful electric tankless water heater designed to provide continuous hot water without interruption, making it an excellent choice for whole-house use. Its 36 kW power and 240V requirement ensure it can handle high demand, delivering water temperatures adjustable between 68°F and 140°F. This allows it to supply multiple showers or appliances simultaneously without running out of hot water. The unit's compact size (around 16.6" wide and 14.5" tall) and wall-mount design save space compared to traditional tank heaters. It also operates silently, which is a nice bonus.

The easy-to-read digital LED display lets you control the temperature precisely, and the internal solid copper heating system provides reliable and efficient heating with auto-modulation to save energy by adjusting power based on water usage. The heater requires substantial electrical capacity—a minimum 300-amp service—which might mean upgrading your home's electrical system if it doesn't already support that. Installation requires hard wiring and professional setup.

A 7-year warranty against leaks and 3-year parts warranty offer peace of mind about durability. This model is well-suited for those seeking an energy-efficient, space-saving, and reliable hot water solution for a medium to large household with adequate electrical infrastructure. Smaller spaces or homes with limited electrical capacity might find it less suitable.