10 Best Tankless Hot Water Heaters 2026 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 RE199eP is a propane-powered outdoor tankless water heater designed to deliver hot water efficiently without running out. It offers a strong flow rate of up to 9.8 gallons per minute, enough to supply several fixtures at once, which is great for larger households or homes with multiple simultaneous water demands. The heater runs on liquid propane and boasts a high heat output of 199,000 BTU, capable of heating water up to 140°F, making it suitable for colder climates where a significant temperature rise is needed. Its compact size, roughly the footprint of a small suitcase, helps save space in outdoor installations.

The system includes a useful LED display that shows service reminders and error codes, which simplifies maintenance and troubleshooting. Energy efficiency is addressed by heating water only when necessary, helping to reduce fuel use and utility costs. On the downside, this model is non-condensing, so it may be less efficient compared to condensing units that recover more heat from exhaust gases. Installation is best left to professionals, especially since it is designed for outdoor mounting and involves propane connections.

The warranty is solid, with up to 15 years on the heat exchanger, giving peace of mind about durability. However, the WiFi control module is not included and must be purchased separately if remote monitoring is desired. This heater is a strong choice for those looking for a reliable, high-capacity propane tankless water heater that balances performance and energy savings, especially in outdoor setups where space and installation conditions matter.

The Rinnai RE180iP tankless water heater is a solid choice if you want a propane model that delivers hot water consistently without taking up much space. It can supply up to 8.5 gallons per minute, which means it can handle multiple fixtures running at once—great for medium to large households. Being propane-fueled, it’s efficient and powerful with a 180,000 BTU rating, but since it’s a non-condensing model, it isn’t as energy-efficient as condensing units. However, its smart design helps conserve energy by heating water only when needed.

The unit is fairly compact—about the size of a small suitcase—and mounts on the wall, saving floor space. It also features an easy-to-read LED display that alerts you to maintenance needs or errors, which can simplify troubleshooting. Installation does require a professional technician, so it’s not ideal if you’re looking for a DIY setup. The heater comes with good warranty coverage: 15 years on the heat exchanger, 5 years on labor, and 1 year on parts, giving peace of mind for long-term use. If you want WiFi control, you’ll need to add the optional controller.

This Rinnai model is well suited for those who want reliable propane heating with a strong flow rate and compact size, provided that professional installation is acceptable and you can accept the slightly lower efficiency compared to condensing heaters.