10 Best Tankless Hot Water Heaters 2025 in the United States

The Rheem RTEX-24 Electric Tankless Water Heater is a solid choice for those seeking an efficient and high-capacity water heating solution. One of its major strengths is its impressive flow rate of up to 5.9 gallons per minute (GPM), which is suitable for serving multiple fixtures simultaneously. Additionally, its 99.8% energy efficiency rating makes it an economical option, as it minimizes energy waste and reduces utility bills.

The electric fuel type ensures ease of installation without the need for gas lines, making it a convenient option for many users. Its compact size (17.63"W x 18.25"H x 3.5"D) and wall-mount capability further enhance its suitability for smaller spaces or areas where floor space is at a premium. The product also boasts a user-friendly digital temperature display and self-modulating power control, which contribute to maintaining consistent and continuous hot water supply on demand.

However, there are some drawbacks to consider. The maximum flow rate may not be sufficient for larger households with high hot water demands during peak usage times. In summary, the Rheem RTEX-24 is an excellent option for small to medium-sized households or professional use, offering high efficiency, ease of installation, and reliable performance within its capacity limits.

The Rinnai RXP199iN is a versatile tankless water heater designed for both indoor and outdoor use, thanks to its Versa Vent system. It runs on either natural gas or propane, which adds flexibility depending on your fuel preference. With a strong flow rate of up to 11.1 gallons per minute, it can supply hot water to around seven fixtures simultaneously, making it suitable for medium to large households. Its energy efficiency is excellent, boasting a UEF (Uniform Energy Factor) of 0.98, which means it uses fuel very efficiently and can help reduce energy bills.

The built-in Smart-Circ recirculation pump is a smart feature that learns your hot water usage patterns and adjusts accordingly, improving efficiency and convenience by reducing wait times for hot water. The water heater is quite compact, about the size of a small suitcase, which helps save space during installation. However, it is fairly heavy at 58 pounds and requires professional installation, which could add to upfront costs. The maximum temperature is 140°F, which fits most household needs. While it offers WiFi connectivity through an optional Control-R module for remote monitoring and control, this is not included and must be purchased separately.

Customer reviews are positive, with a high rating around 4.6 out of 5, reflecting satisfaction with performance and reliability. This Rinnai model is a solid choice for those needing reliable, efficient, and flexible hot water delivery, especially if you want advanced features like smart recirculation and WiFi control. Be prepared for professional installation and consider the additional cost of the WiFi module if desired.

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.