10 Best Outdoor Tankless Water Heaters 2025 in the United States

The Rinnai RXP199iN is a highly efficient tankless water heater that can operate on either propane or natural gas, making it versatile in terms of energy source. With a flow rate of up to 11.1 gallons per minute (GPM), it can supply hot water for multiple fixtures simultaneously, which is great for larger households or outdoor uses where instant hot water is a necessity. Its BTU rating of 199,000 indicates strong heating performance.

One of its standout features is the Smart-Circ Intelligent Recirculation system, which learns your hot water usage patterns and optimizes the recirculation to save energy and reduce wait times for hot water. Additionally, the high energy efficiency rating (UEF .98) means lower operating costs over time.

Installation is an important consideration; while it requires professional installation, the Rinnai Central App offers support for setup and troubleshooting, which can ease the learning curve for users. The heater is also designed for durability and can be installed outdoors with the proper venting, making it suitable for various environments. There are a few potential drawbacks. The need for professional installation may add to the cost, especially for those who prefer DIY projects. The unit is relatively compact but weighs 58 pounds, which might be cumbersome for some to handle during installation. Additionally, while the WiFi connectivity is a modern touch, the Control-R module is sold separately, which may be an extra expense for those wanting smart home integration.

The Rinnai RX199iN Condensing Smart Sense Tankless Water Heater is a solid choice for those seeking an efficient and high-capacity hot water solution for their home. With a flow rate of up to 11.1 gallons per minute (GPM), this heater can handle multiple fixtures simultaneously, making it ideal for larger households or homes with high hot water demand. Its 199,000 BTU rating ensures that it heats water quickly, maintaining a steady supply.

Energy efficiency is a standout feature, boasting a UEF rating of .98, which means it can help lower energy bills compared to less efficient models. The compact design allows for versatile installation, either indoors or outdoors, with the necessary Versa Vent system. This flexibility is a significant advantage for users with limited space.

However, installation isn't a DIY project; it requires professional help, which could add to the overall cost. Additionally, while it has a robust warranty and support system, some users may find the initial purchase price higher than standard water heaters.

The Stiebel Eltron Tankless Water Heater - Tempra 29 Trend is an electric, on-demand water heater that stands out for its continuous hot water flow, meaning your showers won't be interrupted. With a high flow rate of 9.5 gallons per minute (GPM), it is suitable for households needing substantial water supply. Its energy efficiency is notable due to the eco-friendly auto-modulation feature, which adjusts power usage based on demand. The heater has a solid copper heating system, ensuring reliable performance, and operates silently, adding to user comfort. The digital LED temperature display is user-friendly.

In terms of BTU rating, the heater’s heat output is impressive at 28.8 kW, providing significant temperature rise to meet various hot water needs. Installation is simplified as no venting is required, and its compact size saves space. However, it requires a minimum electric service of 200 A, which might necessitate electrical upgrades for some homes. The product's durability is bolstered by its solid construction, though specific weather resistance features for outdoor use are not highlighted, which might be a concern for exposed installations.

The heater benefits from a 7-year leakage warranty and a 3-year parts warranty, offering substantial support for potential issues. In summary, this unit is a strong contender for indoor use and possibly sheltered outdoor setups, providing continuous hot water with high efficiency and minimal noise, though users should consider their electrical infrastructure before purchasing.