10 Best Electric Tankless Water Heater 2025 in the United States

The Rheem 18kW 240V Tankless Electric Water Heater is a solid choice for those looking for an efficient and space-saving water heating solution. One of its standout features is the impressive flow rate of up to 4.4 gallons per minute (GPM), which makes it suitable for smaller households or apartments where demand for hot water isn't excessively high. Its energy efficiency rating of 99.8% is quite remarkable, meaning you'll likely save on your energy bills compared to traditional tank heaters. The self-modulation technology adjusts the power based on hot water demand, which further optimizes energy use.

The external digital control with an LED display is user-friendly, allowing for precise temperature settings within a +/- 1-degree accuracy. This feature is particularly beneficial for those who want to maintain consistent hot water temperatures. The installation is straightforward as well, with bottom connections that make it easier to replace or service when needed.

There are a few drawbacks to consider. While the 4.4 GPM flow rate is adequate for smaller setups, larger families or homes with multiple bathrooms may find it insufficient during peak usage times. Additionally, being an electric unit, it may not be the best option for locations where electricity supply is unreliable or insufficient to support its high wattage of 18,000 watts. Lastly, while the unit is compact, its installation does require adequate space and professional help, especially for wall mounting, which could be a consideration for DIY enthusiasts.

The Rheem RTEX-24 Electric Tankless Water Heater offers a powerful solution for those seeking on-demand hot water. With a 24kW power rating and a maximum flow rate of 5.9 gallons per minute, it is capable of providing continuous hot water for multiple applications simultaneously. The self-modulating power control is a standout feature, allowing for energy-efficient operation by adjusting the power usage based on the actual demand. Additionally, its energy efficiency rating of 99.8% ensures minimal energy wastage, which can lead to lower utility bills over time.

The digital temperature display and ON/OFF dial control make it easy to adjust and monitor the temperature settings, enhancing user convenience. The compact size (17.63 inches wide, 18.25 inches high, and 3.5 inches deep) and wall-mount installation method make it suitable for homes with limited space. However, it is important to note that the unit requires a 240V electrical connection and professional installation is recommended to ensure optimal performance and safety.

While it is a highly efficient and effective water heater, its performance may vary depending on the incoming water temperature and the number of simultaneous hot water demands. Given its robust features, the Rheem RTEX-24 is well-suited for households looking for a reliable and efficient electric tankless water heater but may not be ideal for larger homes with high hot water consumption.

The WINTEMP 36kW tankless electric water heater is designed to provide a steady supply of hot water for whole-house use, with a maximum flow rate of 8.7 gallons per minute. This makes it suitable for multiple showers or faucets running at the same time in an average-sized home. Its 36kW power rating and 240V requirement enable a strong temperature rise, capable of reaching up to 140°F, ensuring warm water even in colder climates.

One of its standout features is energy efficiency; the unit adjusts power based on water flow and temperature, reducing energy use when demand is low and consuming no power when idle. This can lead to significant savings compared to traditional tank water heaters. The compact wall-mounted design saves space and allows for flexible installation, though it requires a substantial electrical setup, including multiple 40-amp breakers and a 300-amp household power supply recommendation. This means installation might be more complex and potentially costly if your home’s electrical system isn’t already configured for it.

Safety features like overheat, leakage, and dry-fire protection, along with ETL certification, add peace of mind. The included WiFi control and LED display make temperature adjustments easy and convenient. Due to the high electrical demand and specialized installation requirements, it is best suited for homes that can support its power needs and for users comfortable with professional installation. For large households seeking endless hot water with good energy savings and space efficiency, this model is a strong contender.