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.

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.

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.