10 Best Tankless Hot Water Heaters 2025 in the United States

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 Stiebel Eltron Tempra 15 Plus is an electric tankless water heater featuring continuous flow technology, which smartly adjusts water flow to maintain a steady temperature without interruptions—ideal for consistent hot showers. Its 14.4 kW power and ability to heat water up to around 140°F suit many household needs, although very large homes with multiple simultaneous uses might find it less powerful.

Its compact, wall-mounted design saves space and does not require venting, which simplifies installation in tight areas. The unit offers strong energy efficiency due to auto-modulation and precise electronic control, helping reduce electrical costs, and it even tracks your energy savings. Operation is straightforward with a digital display and easy temperature presets, while the solid copper heating element ensures durable performance.

This water heater requires a 240-volt, 100-amp electric service, which might necessitate electrical upgrades for some homes. The warranty provides reassurance with 7 years coverage on leaks and 3 years on parts, reflecting confidence in reliability. It is ideal for those seeking an eco-friendly, compact electric solution with stable water temperature but might be less suited for households with very high flow rate demands or limited electric capacity.

The Rinnai CX199iN is a powerful tankless water heater designed for commercial use, delivering a strong flow rate of 11.1 gallons per minute (GPM), which means it can supply plenty of hot water for multiple fixtures at the same time. It operates on natural gas or propane, making it a flexible choice depending on your fuel availability. One of its standout features is its high energy efficiency rating of around 96-97%, which helps lower energy costs compared to traditional water heaters. The unit can raise water temperature up to 185°F, suitable for most commercial needs.

Installation-wise, this model is versatile—it can be mounted indoors or outdoors with the proper venting accessories, and it offers an optional recirculation kit that improves hot water delivery and saves further energy. Its size is relatively compact for its capacity, measuring about 18.5 by 30 inches, and wall mounting helps save floor space. It also includes smart technology for monitoring and managing the heater through an app, which can simplify maintenance and troubleshooting.

A professional installation is recommended, which can add to initial costs. While it boasts many smart features, these may not be necessary for all users and could complicate setup for those less comfortable with technology. Additionally, the price point might be higher than simpler models, reflecting its commercial-grade capacity and efficiency. This water heater suits commercial settings or larger homes needing continuous hot water with efficient energy use. If you want a reliable, high-capacity unit with smart monitoring and flexible installation options, the Rinnai CX199iN is a strong contender. However, if you have simpler needs or a tighter budget, some less complex models might be more appropriate.