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

The Stiebel Eltron Tankless Water Heater - Tempra 29 Trend is an excellent choice for those needing continuous, on-demand hot water. With a flow rate capable of meeting the demands of an entire household, this unit ensures that you never run out of hot water. The 28.8 kW power rating and temperature rise capability from 68° to 140°F means it can handle substantial heating tasks efficiently.

It is also energy efficient, thanks to its auto-modulation feature, which adjusts energy usage based on demand, saving you money in the long run. The compact design of the heater makes it a great space-saving option that can be installed without the need for venting, adding to its convenience. Additionally, the silent operation and easy-to-read digital temperature display enhance user experience.

Installation does require a minimum recommended electric service of 200 A, which might not be suitable for every home. However, the solid copper heating system inside ensures durability and reliability. The product also comes with a 7-Year Leakage and 3-Year Parts warranty, which provides peace of mind regarding its longevity and maintenance. While the installation requirements might be a hurdle for some, the benefits of endless hot water, energy efficiency, and reliable performance make it a strong contender in the category of high-capacity tankless electric hot water heaters.

The Rheem 18kW 240V Tankless Electric Water Heater is tailored for those seeking a reliable and efficient hot water solution in their homes. With a flow rate of up to 4.4 gallons per minute (GPM), it can effectively meet the hot water demands for smaller households or apartments. One of its standout features is the external digital thermostatic control with an LED display, allowing for precise temperature adjustments with 1-degree accuracy, making it user-friendly.

Energy efficiency is another strong point, boasting an impressive efficiency rating of 99.8%. This means it converts nearly all the energy it uses into hot water, which can lead to lower utility bills over time. The self-modulation technology is also advantageous, as it automatically adjusts power to match the required hot water, ensuring you always get what you need without wasting energy.

On the installation front, the Rheem unit is designed with simplicity in mind. It features standard bottom 3/4 inch NPT water connections, making it relatively easy for professionals to install. Its compact size (14.5"W x 18.25"H) allows for wall mounting, which can save space in your utility area. However, while it performs well for smaller applications, larger households may find the flow rate limiting, especially during peak usage times. Additionally, since it's an electric model, users should ensure they have the appropriate electrical setup to support its 18 kW power requirement.

The Stiebel Eltron Tempra 24 Plus is a high-capacity electric tankless water heater designed to provide continuous hot water on demand. One of its standout features is the Advanced Flow Control technology, which ensures a steady water temperature even when multiple outlets are in use. This is a great advantage for families or households with high hot water demand, as it prevents interruptions during showers or while using appliances. Additionally, its compact design makes it a space-saver, and it doesn't require venting, which simplifies installation. The unit is also energy-efficient, utilizing auto-modulation to adjust the energy consumption based on hot water needs, which can lead to savings on energy bills. Users appreciate the digital temperature display and the preset options that enhance ease of use.

However, the Tempra 24 Plus requires a minimum electrical service of 150A, which may necessitate an upgrade for some homes. This can lead to additional installation costs. Although it has a robust warranty of 7 years for leaks and 3 years for parts, some customers might find the upfront expense higher than conventional water heaters.