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 RE180eP is a propane-powered outdoor tankless water heater designed to deliver hot water on demand without storing it. It offers a strong maximum flow rate of up to 8.5 gallons per minute, which is suitable for running multiple fixtures like showers and faucets at the same time in medium to larger households. Being non-condensing, it’s simpler in design but slightly less energy-efficient compared to condensing models, though it still includes features like an LED display to help with maintenance and efficiency reminders.

This model’s compact size, roughly like a small suitcase, makes it easier to install in limited outdoor spaces, but professional installation is recommended to ensure safety and proper setup. It provides a solid temperature rise capacity to meet typical household needs, though exact temperature increase depends on your incoming water temperature and region. The heater comes with a layered warranty—15 years on the heat exchanger, 5 years on labor, and 1 year on parts—to support long-term reliability.

A convenient option is the ability to add WiFi control via an additional module, allowing remote monitoring. This Rinnai unit is a strong choice for those wanting a reliable, high-flow propane outdoor tankless heater with smart features and solid support, while noting it may not be the highest in energy efficiency compared to condensing models.

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.