10 Best Electric Tankless Water Heaters 2025 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 Stiebel Eltron Tempra 20 Plus is an electric tankless water heater designed for consistent on-demand hot water. One of its standout features is the Advanced Flow Control technology, which ensures the water temperature remains steady by slightly reducing flow if the demand exceeds the unit's capacity, meaning hot showers are uninterrupted. This heater has a sleek, compact design that saves space and doesn't require venting, making it suitable for whole-house use.

Plus, it's eco-friendly, thanks to its auto-modulation and electronic water flow control, which helps save energy, and the unit even tracks these savings for you. Operating the Tempra 20 Plus is straightforward with a noise-free electronic switch, digital temperature display, and memory buttons for preset temperatures. The unit requires significant electrical power (19.2kW, 240V, and a minimum 125A service) to operate efficiently, so ensure your home can support this. It offers a wide output temperature range of 68° to 140°F.

The installation is wall-mounted, and the heater itself is relatively light at 20.1 pounds. In terms of warranties, it comes with a 7-year leakage warranty and a 3-year parts warranty, indicating confidence in its durability. Some potential users might find its power requirements and installation needs a bit demanding. If you are looking for a reliable, efficient, and eco-friendly tankless water heater for your home, the Tempra 20 Plus is a strong contender. Just ensure your electrical system can meet its requirements.

The Stiebel Eltron Tempra 29 Plus is a powerful electric tankless water heater designed to deliver a continuous supply of hot water on demand. It offers a maximum flow rate of about 3 gallons per minute, suitable for small to medium households or single-point applications like a shower or sink. Its high wattage (28.8 kW) supports a strong temperature rise, heating cold water efficiently to your desired temperature even in colder climates. The unit includes convenient features like two temperature memory presets and an easy-to-read LED display for simple control.

Installation requires a dedicated hard-wired 240-volt electric supply with three separate 40-amp breakers and substantial wiring, as well as a home electrical service of at least 200 amps. This means it might require an electrical upgrade if the home’s system is not already equipped, which could add to initial costs and complexity. The heater’s compact size and wall-mount design save space, and no venting is needed, making it easier to install in various locations.

Energy efficiency is high due to the on-demand heating technology, which only heats water when needed, reducing wasted energy compared to traditional tank heaters. The unit weighs 24 pounds and comes with certifications ensuring safety and quality. This model is ideal for homeowners seeking efficient, space-saving hot water solutions who have the electrical capacity or are willing to upgrade their system. It may be less suitable for very large households needing multiple hot water outlets simultaneously or for those without access to the required electrical setup.