10 Best Tankless Electric Hot Water Heaters 2025 in the United States

The Rheem RTEX-24 24kW 240V Electric Tankless Water Heater is a commendable option for delivering on-demand hot water. With a flow rate of up to 5.9 gallons per minute (GPM), it can handle multiple fixtures simultaneously, making it suitable for larger households or high-demand situations.

The adjustable digital temperature display and self-modulating power control allow for precise temperature management and efficient energy use, contributing to its impressive 99.8% energy efficiency rating. This can help to reduce electricity bills over time. Installation is relatively straightforward with its wall mount design and bottom 3/4" NPT water connections, though professional installation is recommended to ensure optimal performance and safety.

The unit's compact dimensions (17.63" wide, 18.25" high, and 3.5" deep) make it a good fit for tight spaces. However, its power requirements (240 volts and 24kW) necessitate a substantial electrical setup, which may not be suitable for all homes without electrical upgrades. The Rheem RTEX-24 offers a robust and energy-efficient solution for consistent and continuous hot water, with some considerations regarding electrical requirements.

The Stiebel Eltron Tempra 29 Trend is an electric tankless hot water heater designed to provide on-demand hot water efficiently, making it a great choice for homeowners looking to upgrade their water heating system. One of its standout features is the continuous flow capability, which allows for unlimited hot water without interruption, ensuring you can enjoy long showers or multiple fixtures running simultaneously without running out of hot water. The small and sleek design means it won't take up much space, and since it doesn't require venting, it simplifies installation.

Energy efficiency is a strong point for the Tempra 29 Trend, thanks to its auto-modulation feature, which adjusts power use based on demand, potentially lowering energy bills. It operates silently, which can be a big plus for households sensitive to noise. The digital temperature display is user-friendly, allowing for easy adjustments and monitoring.

The product does have some limitations. It requires a significant electric service of 200 A, which may mean additional electrical upgrades for some homes. Also, while it performs well for many applications, larger households or simultaneous high-demand scenarios might find its maximum output of about 9.5 gallons per minute a bit limiting, especially when multiple outlets require hot water at once.

Warranty options are solid, with a 7-year leakage warranty and a 3-year parts warranty, giving customers peace of mind regarding reliability. This tankless water heater is well-suited for medium to large households that value space-saving designs and energy efficiency, but prospective buyers should ensure their electrical systems can accommodate the power requirements for optimal performance.

The Rheem 18kW 240V Tankless Electric Water Heater is designed for those looking for an efficient and space-saving hot water solution. With a flow rate of up to 4.4 gallons per minute, it can adequately meet the hot water demands of small to medium-sized households. Its self-modulating feature intelligently adjusts the power based on your hot water needs, ensuring energy efficiency, with an impressive efficiency rating of 99.8%. This can lead to cost savings on energy bills over time.

One of its highlights is the external digital thermostatic control with an LED display, which allows for precise temperature adjustments within a degree. This user-friendly interface makes it easy to monitor and set your preferred water temperatures. Installation is a breeze as well, thanks to its wall-mountable design and straightforward connection options, making it a suitable choice for DIY enthusiasts or professional installations alike. The compact size ensures it won't take up much space, making it ideal for areas where a traditional tank heater would be cumbersome.

However, there are some considerations to keep in mind. While the flow rate is satisfactory for many, larger households or those with high simultaneous usage may find it inadequate, especially during peak demand times. Additionally, the requirement for a dedicated 240V electrical connection may necessitate an upgrade if your current setup is not compatible. The Rheem 18kW unit is a solid choice for users seeking a compact and effective tankless electric water heater, but it may not be the best fit for larger families or high-demand situations.