10 Best Tankless Hot Water Heaters 2025 in the United States

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 Ranein Natural Gas Tankless Water Heater delivers a flow rate of 3.6 gallons per minute, sufficient to supply hot water simultaneously to about two or three spots like a bathroom and kitchen. Thanks to its 80,000 BTU heating power, it provides instant hot water without the long wait common with traditional tanks. It’s designed for indoor use and includes useful safety features such as dry combustion and flame failure protection.

One standout feature is the four temperature modes tailored to different needs, like dishwashing or bathing infants, adding convenience. Installation-wise, it comes with an exhaust pipe and standard fittings which helps save extra costs, but it’s important to have it installed by a licensed professional following local codes. The unit is compact enough to fit on a wall, making it suitable for homes with limited space.

However, it’s not recommended for high altitude areas over 2,000 feet, which could limit where it’s used. If you want a natural gas heater that saves space, offers immediate hot water, and covers basic household needs, this is a practical choice, though checking your local installation requirements is important.

The Rinnai V75IN is a natural gas tankless water heater designed for indoor use, delivering a flow rate of up to 7.5 gallons per minute (GPM). This means it can efficiently provide hot water to around five appliances at the same time, making it suitable for medium-sized homes or households with moderate hot water demand. Its compact size (30" wide by 13" high) helps save space compared to traditional tank heaters.

In terms of energy efficiency, it has a solid Energy Factor of 0.82, which means it uses gas efficiently by heating water only when you need it, reducing waste and utility costs. The unit also features leak detection to prevent water damage and a temperature range adjustable between 98ºF and 140ºF, offering good control to match your comfort preferences. Installation is intended to be professional, which is important as improper setup can affect performance and safety. The heater runs on natural gas, a common and generally cost-effective fuel choice. Warranty protection includes 10 years on the heat exchanger, 5 years on labor, and 1 year on parts, which provides confidence in the product's durability and support.

Some potential drawbacks include the 7.5 GPM flow rate which might be limiting for larger households with high simultaneous hot water needs. Additionally, the requirement for professional installation adds to initial costs and complexity. The temperature range may not suit users wanting water temperatures above 140ºF, though this limitation is typical for safety reasons. The Rinnai V75IN delivers reliable, energy-efficient hot water with a good flow rate for most average homes, especially those preferring natural gas and seeking space savings. Consider its flow capacity and installation requirements to determine if it meets your household needs.