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 Rheem RTG-84XLN-3 is a high-efficiency, non-condensing outdoor tankless natural gas water heater designed to provide continuous hot water. With a maximum flow rate of 8.4 gallons per minute, this unit can supply enough hot water for multiple applications simultaneously, such as showers and dishwashers, making it ideal for larger households. It is also designed to save on energy costs by only running when needed, and its water-saving setting can save up to 1,100 gallons of water per year. Additionally, its hot-start programming helps avoid cold-water bursts by keeping the heater in a ready state.

The Rheem RTG-84XLN-3 is 19% smaller and 22% lighter than previous models, which simplifies installation and saves space. It has a maximum temperature of 140 degrees Fahrenheit and is certified for high efficiency by GAMA. The unit is designed for outdoor installation and mounts on a wall, making it convenient for homeowners who want to save indoor space. The product dimensions are 13.5 inches by 20.75 inches, and it weighs 39.2 pounds.

Some potential drawbacks include its reliance on natural gas, which may not be suitable for all homes, and the need for professional installation. Additionally, while the unit is efficient, it may not perform as well in extremely cold climates where higher temperature rises are needed. However, for most households looking for a reliable and space-saving tankless water heater, the Rheem RTG-84XLN-3 appears to be a strong contender.