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 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.

The Rinnai RX130iN tankless water heater is a solid choice for anyone needing a reliable hot water supply indoors or outdoors. It delivers up to 7.1 gallons per minute, which means it can handle around four fixtures running at the same time without running out of hot water. The 130,000 BTU rating indicates strong heating power capable of raising water temperature efficiently, even for larger households or homes with colder incoming water. One standout feature is its high energy efficiency, with a UEF of 0.97, meaning it uses fuel very effectively and can help save on energy bills. Installation is simplified by the Versa Vent system, allowing the unit to be safely installed indoors or outside, although outdoor installation requires an extra vent cap. Weather resistance is implied by its design for outdoor use, but professional installation is strongly recommended to ensure safety and longevity.

The water heater comes with smart gas control for precise temperature management and a user-friendly interface, plus WiFi control is an option if you add the Controlr module. At 19 by 31 inches and weighing 54 pounds, it is compact but sturdy. The warranty and support from Rinnai, along with their online resources and professional installer network, add peace of mind. One downside is that the WiFi feature is not included and the initial cost and installation may be higher due to professional requirements. Also, while suitable for outdoor use, harsh climates may still require additional protection.

If you want a compact, energy-efficient unit that can be installed flexibly and handle multiple water outlets, this model fits well, especially for families or homes with moderate to high hot water needs.