Thinking about installing a tankless water heater outside? Outdoor tankless water heaters save indoor space, eliminate the need for venting, and are perfect for mild to moderate climates. But they come with unique installation needs and weather protection requirements. This guide explains everything you need to know about using a tankless water heater outdoors—plus the best models, pro tips for a smooth install, and what to watch out for to keep your hot water flowing year-round.
Quick Picks: Best Outdoor Tankless Water Heaters
-
Best Overall:
Rinnai V75EN Outdoor Natural Gas Tankless Water Heater – High flow, reliable freeze protection, trusted for whole-house use. -
Best for Large Families:
Rheem RTG-95XLN Outdoor Tankless Water Heater – Up to 9.5 GPM, built to withstand harsh conditions. -
Best Budget:
Camplux 5L Outdoor Propane Tankless Water Heater – Great for cabins, outdoor showers, and backup hot water.
Why Install a Tankless Water Heater Outside?
- No Venting Required: Outdoor models vent directly to open air, making installation simpler and cheaper.
- Save Indoor Space: Perfect for small homes, apartments, garages, or anywhere indoor wall space is tight.
- Easy Access: Service and repairs are a breeze, with everything right outside your home.
- Great for Mild to Moderate Climates: Outdoor models work year-round in most US regions, with built-in freeze protection for mild freezes.
Outdoor Tankless Water Heater: Buyer’s Guide
- Climate Rating: Check the lowest temps your model can handle—most outdoor tankless units have freeze protection down to -20°F, but extreme climates may need extra steps.
- GPM (Gallons Per Minute): Choose a heater with enough flow for your household—bigger families or homes with tubs/showers running at once need 7–10 GPM.
- Fuel Type: Outdoor tankless models are typically natural gas or propane. Electric units are almost always indoor only.
- Weatherproof Casing: Look for heavy-duty, rust-resistant, and weatherproof construction.
- Freeze Protection: Built-in electric heaters keep components from freezing. Must be plugged in and tested yearly.
- Installation: Wall-mount to a sturdy exterior wall, connect to gas and water lines, and ensure rain/snow can’t collect in or around the unit.
- Warranty: Longer warranties protect your investment—look for 5–12 years on heat exchangers.
How to Install and Protect an Outdoor Tankless Water Heater
- Choose a Sheltered Spot: Install under an eave or awning when possible to reduce weather exposure.
- Use Approved Mounting Hardware: Secure to a masonry or studded wall—never install directly on vinyl or siding alone.
- Plumbing: Use insulated and UV-resistant pipe insulation on all outdoor lines. Install shut-off valves and unions for easy servicing.
- Gas Connection: Use a licensed plumber to run and connect gas lines safely and to code.
- Freeze Protection: Plug in the built-in heater, and consider pipe heating cables in the coldest climates. Drain the unit if power will be off during a freeze.
- Test Operation: Run water and confirm hot water at every fixture. Check for leaks, listen for odd noises, and monitor for error codes.
Tip: In climates with deep winter freezes, install a bypass/drain kit so you can winterize your heater if needed.
Detailed Reviews: Top Outdoor Tankless Water Heaters
Rinnai V75EN Outdoor Natural Gas Tankless Water Heater
- 7.5 GPM, reliable performance for up to 3–4 showers at once
- Durable outdoor casing, built-in freeze protection to -22°F
- Energy Star qualified and super-efficient
- 10-year heat exchanger warranty
Pros:
- Rock-solid reliability and safety features
- Runs quiet and needs no venting
- Trusted brand with strong support
Cons:
- Professional installation recommended
- Must be plugged in for freeze protection
Final Verdict: The top choice for most homes needing powerful, hassle-free outdoor hot water.
See it on Amazon
Rheem RTG-95XLN Outdoor Tankless Water Heater
- 9.5 GPM, perfect for 4+ bathrooms or simultaneous use
- Stainless steel, freeze protection, and digital controls
- Energy Star rated, 12-year heat exchanger warranty
Pros:
- Super-high flow and efficiency
- Weatherproof for most climates
- Trusted warranty and US support
Cons:
- Larger unit—needs sturdy wall space
- Higher up-front investment
Final Verdict: Best premium option for large families or high-demand homes.
Check price on Amazon
Camplux 5L Outdoor Propane Tankless Water Heater
- 1.32 GPM, perfect for cabins, camping, outdoor showers, or as a backup
- Portable, lightweight, runs on propane
- Easy setup and quick hot water outdoors
Pros:
- Very affordable
- Lightweight and portable
- Great for DIYers and seasonal use
Cons:
- Not for whole-house use
- No built-in freeze protection
Final Verdict: The best portable outdoor tankless—great for showers, RV, or emergencies.
See details on Amazon
Comparison Table: Best Outdoor Tankless Water Heaters
| Model | Max GPM | Fuel | Freeze Protection | Warranty | Best For | Price Link |
|---|---|---|---|---|---|---|
| Rinnai V75EN | 7.5 | Natural Gas | Yes (-22°F) | 10 yr HEX | Most homes | View |
| Rheem RTG-95XLN | 9.5 | Natural Gas | Yes | 12 yr HEX | Large family | View |
| Camplux 5L | 1.32 | Propane | No | 1 yr | Cabin/portable | View |
FAQ: Outdoor Tankless Water Heaters
- Can you really run a tankless water heater outside year-round?
Yes, if it’s built for outdoor use and has freeze protection. In extreme cold, extra steps like draining or pipe heat cables may be needed. - What happens if the power goes out in winter?
Freeze protection won’t work without power. Always drain the heater or use a battery backup if outages are possible in freezing weather. - Is maintenance different than indoor models?
No, you still need to flush and descale yearly. Inspect for leaves, bugs, and weather damage as part of routine checks. - Can I install it myself?
Portable units, yes. For permanent outdoor tankless, use a licensed plumber for gas, water, and mounting to ensure warranty and safety. - Are these more likely to freeze?
They are designed for outdoor use, but any water line or heater can freeze if not properly protected in severe cold.
Conclusion
Installing a tankless water heater outside is a smart way to save space and simplify venting—just pick a model rated for your climate and needs. With the right setup and maintenance, outdoor tankless heaters offer reliable, energy-efficient hot water for years to come. Ready to upgrade? Choose from the top models above, follow our pro tips, and enjoy hot water—rain, shine, or snow!