10 Best Electric Tankless Hot Water Heater 2026 in the United States

The Rheem RTEX-24 is a solid choice for anyone looking for an electric tankless water heater, particularly for residential use. One of its key strengths is its impressive flow rate of up to 5.9 gallons per minute, making it suitable for medium to large households where multiple hot water outlets may be used simultaneously. Its self-modulating power control ensures that the heater adjusts energy use based on demand, which can help in energy savings. With an energy efficiency rating of 99.8%, this unit can significantly reduce your utility bills compared to traditional tank heaters.

The adjustable digital temperature display is user-friendly, allowing for easy temperature adjustments to find that just-right warmth. The compact design, with dimensions that allow for wall mounting, can save space in smaller homes.

There are a few considerations to keep in mind. The installation might require a professional, especially if you’re not handy, as it involves electrical connections that must be done correctly for safety. Additionally, while the heater’s specifications are strong, it may struggle if you have high hot water demands at multiple points at once, depending on the temperature rise needed and your incoming water temperature. Lastly, Rheem provides a warranty, but it's always good to check the specifics to ensure you’re covered in case of any manufacturing defects. If you’re seeking a reliable and efficient hot water heater for your home, the Rheem RTEX-24 is certainly worth considering.

The Rheem 18kW 240V Tankless Electric Water Heater is designed to offer an on-demand hot water solution for homeowners looking to save space and energy. With a flow rate of up to 4.4 gallons per minute (GPM), it can efficiently supply hot water for multiple outlets at once, making it suitable for medium-sized households or apartments. One standout feature is its external digital thermostatic control with a precise +/- 1 degree accuracy, allowing users to easily set their desired water temperature.

The self-modulation technology adjusts the power based on your hot water needs, optimizing energy use and maintaining efficiency, which is an impressive 99.8%. This means you can enjoy hot water without worrying too much about energy bills.

Installation is relatively straightforward with its wall-mount design and 3/4 inch NPT connections which simplify the setup process. The durable copper heating elements are also field-serviceable, contributing to the unit’s longevity. There are a few drawbacks to consider. The unit requires a 240V power supply and an adequate electrical setup, which might necessitate professional installation if your home isn’t equipped. It may not be powerful enough for larger households or homes with high demand for simultaneous hot water use.

The Stiebel Eltron Tempra 36 Plus is a powerful electric tankless water heater designed to deliver continuous hot water on demand. Its 36 kW power allows it to heat water quickly, supporting a flow rate of about 1.5 gallons per minute, which is suitable for small to medium household needs, such as one or two bathroom uses simultaneously. The heater can raise water temperature up to 140°F, comfortably covering most typical hot water requirements. One key feature is Advanced Flow Control, which maintains steady water temperature even when demand changes, helping to avoid sudden cold or hot bursts.

The unit is energy efficient thanks to self-modulation technology that adjusts power use based on demand, reducing electricity waste. It requires a 240-volt hardwired connection and has a relatively compact wall-mounted design (about 16.6" wide and 14.5" high), making installation feasible in many homes but potentially requiring professional support due to the electrical setup. The copper construction adds durability, and the digital LED display allows for simple and precise temperature adjustments. Stiebel Eltron is known for reliable products that provide peace of mind.

The flow rate might be limiting for larger households or simultaneous multiple heavy uses, and the need for a high-voltage electrical connection could result in additional installation costs. This model is well suited for users seeking an efficient, reliable electric tankless water heater with consistent temperature control for moderate hot water demands.