10 Best Tankless Hot Water Heaters 2025 in the United States

The Rheem 18kW 240V Tankless Electric Water Heater in Gray offers several appealing features for those in need of a compact and efficient water heating solution. The primary advantages of this model include its advanced self-modulation technology, which helps adjust power based on the hot water demand, ensuring energy efficiency and cost savings. Additionally, it boasts a flow rate of up to 4.4 GPM, which is suitable for small to medium households, providing enough hot water for multiple uses simultaneously.

The external digital thermostatic control with an LED display allows for precise temperature adjustments, enhancing user convenience and comfort. The heater is also equipped with durable copper immersion heating elements, which are field serviceable, making it easier to maintain and extend its lifespan. Installation is straightforward due to the bottom 3/4 inch NPT water connections and threaded design, allowing for easy replacement if necessary.

However, there are some drawbacks to consider. As an electric heater, it may not be as efficient or cost-effective in areas with high electricity rates compared to gas-powered models. Additionally, the temperature rise might be limited in very cold climates, potentially affecting the heater's performance. The size and installation process, while simple, may still require professional assistance for those unfamiliar with electrical systems. Lastly, it's essential to review the warranty and support options from Rheem to ensure long-term reliability. The Rheem 18kW 240V Tankless Electric Water Heater is a strong choice for individuals seeking an energy-efficient, easy-to-use, and maintain water heating solution within the limitations of an electric-powered system.

The Rinnai RX199iN is a powerful tankless water heater that stands out for its impressive flow rate of up to 11.1 gallons per minute, making it suitable for homes with multiple fixtures needing hot water simultaneously. It's designed to operate on either natural gas or propane, giving you flexibility depending on your fuel source. The energy efficiency is top-notch, boasting a UEF rating of .98, which means it uses energy very effectively, potentially saving you on utility bills.

One of the great features is its compact size, comparable to that of a small suitcase, making it easier to fit into various spaces. The Smart Sense gas control system adds convenience, allowing for easier operation. However, the installation of this unit is recommended to be done by a professional. While this ensures safety and proper functionality, it could increase your expenses if you don’t have a technician readily available.

While its high efficiency is a significant advantage, it may not be the best choice for all water temperature needs depending on your region’s groundwater temperature. Additional considerations include the need for the RX-OVC vent cap for outdoor installation, which adds to the installation complexity and cost. Also, the Controlr module for WiFi control is sold separately, which might be a drawback for those looking for smart home integration right out of the box. If you are looking for a tankless heater that offers high performance and efficiency, the Rinnai RX199iN is a strong contender. Just ensure you’re prepared to handle the installation requirements and additional features you may want to consider.

The EcoSmart ECO 11 electric tankless water heater is a compact and energy-efficient choice ideal for small spaces like bathrooms, office breakrooms, or point-of-use applications. It delivers continuous hot water on demand without the need for a storage tank, which helps save energy since it only heats water when needed. With a maximum flow rate of about 3.1 gallons per minute, it works well for low-demand situations, but it might struggle if you need to run multiple showers or faucets at the same time.

Operating at 240 volts with a 13kW power rating, it offers a reliable temperature rise, maintaining water temperature within 1 degree of your setting thanks to its self-modulating technology. Installation is straightforward since it’s wall-mounted and quite small compared to traditional heaters, saving valuable space in your home. The heater also features an easy-to-read LED display for monitoring settings. One thing to keep in mind is the relatively high amperage draw (54 A), so your electrical setup needs to support that.

The lifetime warranty on electronics and heating elements is a nice reassurance, although it doesn’t cover installation costs or incidental damages. If you need a compact, efficient, and simple tankless water heater for light use or a single bathroom, this model makes a solid choice. For larger households or heavy hot water users, a unit with a higher flow rate would be more suitable.