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

The Stiebel Eltron Tempra 29 Trend is a solid choice for those seeking a reliable and efficient tankless electric hot water heater for their home. One of its main strengths is its continuous flow feature, which ensures that you never run out of hot water, making it ideal for families or households with high hot water demands. With a maximum flow rate of 9.5 gallons per minute, it can easily handle multiple tasks simultaneously, like showering and washing dishes.

Its energy efficiency is another highlight. The auto-modulation feature means the heater adjusts its power output based on the demand, saving energy when hot water is not being used. This eco-friendly design is a great benefit for those looking to minimize their environmental impact and utility bills.

In terms of installation, the compact design requires no venting and can be mounted on the wall, saving valuable space. However, it does require a minimum electrical service of 200 A, which might necessitate an upgrade for some households. The Tempra 29 Trend operates silently, enhancing user experience, especially in quiet home settings. The digital temperature display is easy to read, adding convenience when adjusting settings.

The Rheem 18kW 240V Tankless Electric Water Heater is a solid choice for those looking for a reliable hot water solution, especially in outdoor settings. With a maximum flow rate of 4.4 gallons per minute, it’s well-suited for moderate demand, making it ideal for small to medium-sized households or outdoor applications where hot water is needed intermittently.

One of the standout features is its external digital thermostatic control with a clear LED display, allowing for precise temperature adjustments. The advanced self-modulation technology helps manage energy use effectively, which can lead to savings on electricity bills. Its impressive energy efficiency rating of 99.8% means you’re getting almost all the energy converted into hot water, which is great for eco-conscious users.

The installation process is user-friendly, thanks to the bottom 3/4 inch NPT water connections and the wall-mount design, making it a practical option for those who might consider a DIY installation. The durable copper heating elements are another plus, designed for longevity and ease of service.

The Stiebel Eltron Tempra 36 Trend offers a practical solution for those seeking a tankless electric water heater that provides on-demand hot water. It ensures a continuous flow, meaning you won't run out of hot water during long showers, which is a significant advantage for families or households with higher water demands. With a powerful 36kW capacity, it can support a temperature rise from 68° to 140°F, making it suitable for various climates and use cases. However, the flow rate is on the lower side at 0.77 GPM, which might not suffice if multiple water outlets are used simultaneously.

This model is energy efficient, benefiting from an eco-friendly design and auto-modulation to conserve energy when not in use. Its compact size makes it a space-saving option that can be wall-mounted without requiring venting, simplifying installation. However, it demands a substantial electrical service of 300A, which might necessitate an electrical system upgrade in some homes.

The Tempra 36 Trend operates silently, and its digital temperature display is user-friendly, enhancing its appeal for home use. Constructed with a solid copper heating system, it promises durability, and the included warranties—a 7-year leakage and 3-year parts guarantee—further attest to its reliability. Weighing 22.5 pounds, its installation is relatively straightforward, although professional installation is recommended to deal with its high power requirements. While it ranks well in customer satisfaction, as seen in its 4.5-star rating, potential buyers should consider their home’s electrical capacity and water demand requirements before purchasing. This heater is particularly well-suited for single-family homes looking for an eco-friendly, space-efficient hot water solution.