If you live in a home where space is tight or you prefer to keep mechanical equipment out of the house, a gas tankless water heater for outdoor installation can be the perfect solution. These units mount outside, saving indoor space, and they’re designed to handle the elements while still delivering endless hot water on demand.
In this guide, we’ll explore the top gas tankless water heaters for outdoor use in 2025, what makes them stand out, and how to choose the right one for your home. Toward the end, we’ll also talk about an often-overlooked part of your plumbing system that could save you from thousands of dollars in unexpected repair bills.
Why Choose an Outdoor Gas Tankless Water Heater?
Installing your gas tankless heater outdoors offers several advantages:
- Space saving: Frees up indoor utility space for storage or other equipment.
- No indoor venting required: Outdoor units vent naturally, avoiding complex venting systems.
- Easy access for maintenance: Technicians can work on the unit without entering your home.
- Quieter operation indoors: Any noise from the unit stays outside.
Of course, outdoor units must be designed for weather resistance, so choosing the right model is essential.
Best Overall Outdoor Gas Tankless Water Heater: Rinnai RL75eN
For years, Rinnai has been a leader in gas tankless technology, and their RL75eN is one of the top-rated outdoor natural gas models for 2025. It’s powerful, reliable, and built to withstand the elements.
- Up to 7.5 gallons per minute (GPM) – enough for two to three showers at once.
- ENERGY STAR® certified for efficiency.
- Durable, weather-resistant casing.
- Freeze protection down to -22°F with proper installation.
It’s a great choice for mid-sized households who want dependable hot water without taking up indoor space.
Other Top Outdoor Gas Tankless Water Heaters
Noritz EZTR50 Outdoor
Noritz is known for its easy installation, especially for replacing old tank heaters. The EZTR50 Outdoor offers a strong GPM, energy efficiency, and excellent performance in cold climates.
Rheem Performance Platinum Outdoor 9.5 GPM
Rheem’s outdoor gas unit combines high output with smart Wi-Fi controls, allowing you to monitor and adjust temperature from your phone. Perfect for larger households.
Navien NPN-Universal Outdoor
Navien’s NPN series can be installed either indoors or outdoors, giving flexibility. The outdoor configuration includes weatherproofing and freeze protection while maintaining high efficiency.
Bosch Greentherm 9000 Outdoor
Bosch brings German engineering to the table with a durable, sleek design. The outdoor model is energy-efficient and ideal for moderate climates.
Key Features to Look For in an Outdoor Gas Tankless Heater
When shopping for an outdoor model, consider these factors:
- Flow rate (GPM): Match to your peak household demand.
- Climate compatibility: Ensure the unit has freeze protection if you live in cold areas.
- Fuel type: Confirm the unit is compatible with your natural gas or propane supply.
- Weather resistance: Look for corrosion-resistant casings and waterproof seals.
- Warranty: Outdoor exposure means durability matters even more.
Pro Tip: Even outdoor units benefit from a protective cover or alcove to shield them from extreme conditions.
Installation Considerations
Outdoor gas tankless heaters require professional installation to ensure proper gas line connection, secure mounting, and safe water connections. Placement matters—install in a location that is accessible, sheltered from direct rainfall, and within a reasonable distance of your plumbing system to reduce heat loss.
Maintenance for Outdoor Units
Outdoor units are designed to last, but they still need regular care:
- Flush the system annually to prevent mineral buildup.
- Check the casing and seals for signs of wear or damage.
- Inspect the freeze protection system before winter.
With proper maintenance, a quality outdoor gas tankless water heater can last 15–20 years.
The Overlooked Side of Your Plumbing System
Installing a new outdoor gas tankless heater solves your “hot water in” problem, but what about the “water out” side? If you have a septic tank, it’s crucial to keep it healthy. Increased hot water usage can strain an already struggling septic system, leading to slow drains, foul odors, and costly repairs.
Unfortunately, many homeowners ignore septic care until it’s too late—when repairs can run into thousands of dollars.
SEPTIFIX – Protect Your Septic System
SEPTIFIX is the #1 septic tank treatment in the US, trusted by homeowners to keep their systems running smoothly. These small tablets dissolve in your toilet, releasing oxygen and beneficial bacteria to break down waste, sludge, and grease.
Benefits include:
- Eliminates foul odors within days.
- Prevents costly backups and pump-outs.
- Safe for all septic systems and environmentally friendly.
- Easy to use—just flush one tablet each month.
Pairing your new outdoor gas tankless heater with regular SEPTIFIX treatment ensures your home’s entire water system stays in peak condition.
Final Thoughts
In 2025, the Rinnai RL75eN is our top pick for the best outdoor gas tankless water heater thanks to its strong performance, durability, and weather protection. However, excellent alternatives like the Noritz EZTR50 Outdoor, Rheem Performance Platinum Outdoor, Navien NPN-Universal Outdoor, and Bosch Greentherm 9000 Outdoor offer great options depending on your household size, climate, and budget.
And remember—hot water is only part of the equation. Protecting your septic system with SEPTIFIX means you’ll enjoy trouble-free plumbing for years to come.
Order SEPTIFIX Today – Keep Your Septic Tank Clean and Odor-Free
Endless hot water without septic problems? That’s the true definition of comfort.