Looking for an exterior tankless water heater that delivers reliable hot water for your home? This guide compares top exterior units, highlighting which configurations fit homes with multiple outlets, high demand, or compact outdoor spaces. Each option is evaluated for best use case, installation practicality, and potential limits so you can choose confidently.
Buyer profiles at a glance:
– Whole-house comfort seekers: APUS 190,000 BTU (8.1 GPM) and Rheem RTG-84XLN-3 (8.4 GPM) excel for 2–3 bathroom homes.
– Compact outdoor spaces: Rinnai REP199eN and ORBEK offer strong performance with space-conscious designs.
– Value-driven outdoor setups: Ranein and the mid-range Rheem RTG-70XLN-3 provide balanced flow with solid efficiency.
Quick comparison
- APUS 190,000 BTU: Best for high simultaneous hot-water needs outdoors.
- Rheem RTG-84XLN-3: Better for homes with multiple bathrooms and steady peak demand.
- ORBEK Natural Gas Tankless: Choose this if you need reliable low-flow startup and compact footprint.
- Rinnai REP199eN: Best for recirculation-enabled convenience in larger homes.
- Ranein Natural Gas Tankless: Best value with straightforward outdoor setup and decent flow.
APUS 190k BTU Outdoor Tankless: High-Flow For Whole Home
The APUS unit delivers 190,000 BTU and 8.1 GPM, making it suitable for whole-house use with multiple outlets. It supports 3 showers plus 2 faucets simultaneously and maintains stable performance with low water flow. Best for buyers needing robust outdoor heat without indoor space use and for homes with higher simultaneous demand.
Best for: households with several simultaneous hot-water needs and outdoor installation. Caution: installation requires outdoor power and proper venting; verify gas line compatibility before purchasing.
Rheem RTG-84XLN-3 High Efficiency Outdoor Tankless
This unit provides up to 8.4 GPM and 180,000 BTUs, designed for outdoor installation and reliable hot water for 2–3 bathroom homes. Its durable cabinet supports easy external mounting by a professional. Best for: homes with multiple bathrooms needing quick, steady hot water during peak use. Caution: outdoor exposure requires weatherproofing and proper clearances, and installation should be performed by a qualified installer.
Best for: higher simultaneous demand in medium-to-large homes. Better for: outdoor-ready installations with wall-mount capability. Avoid: settings with very low outdoor temperatures if not rated for cold-climate use.
ORBEK Natural Gas Tankless: 5.1 GPM Outdoor Model
The ORBEK unit offers 120,000 BTU with 5.1 GPM and a low-flow start technology. It can serve 2–4 outlets with a strong temperature stability (±1°F) due to fast dynamic control. Best for: smaller homes or where outdoor space constraints require a compact unit. Caution: 0.53 GPM low-flow start may still require moderate flow to begin heating for some taps.
Best for: compact outdoor setups with reliable temperature stability. Choose this if: you want a balanced outdoor model with good efficiency at lower flows. Avoid: very high simultaneous demand without verifying GPM compatibility.
Rinnai REP199eN Smart-Circ Outdoor Tankless
This model features Smart-Circ Intelligent Recirculation for energy efficiency by learning your water usage patterns. It delivers up to 7.9 GPM and up to 199,000 BTU with outdoor installation compatibility. Best for: homes that benefit from built-in recirculation to reduce wait time for hot water. Caution: control modules for WiFi are not included and may require additional components.
Best for: households seeking convenient instant hot water and reduced wait times. Better for: homes with longer plumbing runs or guest rooms where recirculation saves time. Avoid: relying on the unit’s WiFi control if you rely on standard, non-connected setups.
Ranein Natural Gas Tankless Outdoor: 8.5 GPM
The Ranein outdoor unit provides up to 8.5 GPM with 190,000 BTU. It emphasizes safe operation with features like automatic fuel supply adjustments and a compact footprint. Best for: homes needing straightforward outdoor installation with robust performance. Caution: check local venting and gas line requirements, as data suggests a larger footprint than some compact models.
Best for: solid outdoor performance with straightforward setup. Choose this if: you want reliable flow without extreme space demands. Avoid: installations with very tight outdoor spaces or restricted venting options.
Rheem RTG-70XLN-3 High Efficiency Outdoor
Delivering up to 7.0 GPM and 160,000 BTU, this model suits outdoor needs for homes with moderate hot-water demand and multiple fixtures. It features a durable cabinet and is designed for outdoor installation with easy mounting. Best for: homes that require dependable hot water with a budget-friendly outdoor heater. Caution: lower GPM than some high-demand models means potential limit during peak usage.
Best for: practical outdoor installation with steady performance. Better for: smaller or mid-sized homes with standard hot-water needs. Avoid: very high simultaneous demand where higher GPM is beneficial.
Buying Guide: Exterior Tankless Water Heater Considerations
- Location and installation: Exterior models require weatherproofing, proper clearance, and electrical and gas line access. Confirm clearances from walls, doors, and windows.
- Gas type and capacity: Choose between natural gas and propane. Ensure BTU rating aligns with your home’s hot-water needs and gas supply capacity.
- GPM and outlet needs: Estimate simultaneous usage (showers, sinks, laundry). Higher GPM supports more outlets at once but may need larger gas supply.
- Flow start at low pressure: Some units start heating at very low flows; others require higher flows to engage. Match to your typical water usage patterns.
- Outdoor durability: Look for weatherproof housings and corrosion resistance for prolonged outdoor exposure.
- Recirculation options: Built-in or compatible recirculation features can reduce wait time for hot water in large homes.
- Maintenance and service: Consider units with accessible service panels and straightforward replacement parts. Confirm warranty terms with installers.
Frequently Asked Questions
What is an exterior tankless water heater?
A heater installed outside the home that heats water on demand without a storage tank, helping save space and reduce standby heat loss.
Is higher GPM always better?
Higher GPM supports more simultaneous outlets, but requires greater gas supply and airflow. Choose based on your home’s peak water needs.
Do exterior models require special venting?
Most exterior gas models vent through the venting system built into the unit or via outdoor-specific venting; follow local code and installer guidance.
Can these units provide hot water to multiple bathrooms at once?
Yes, when sized for your demand. Models like 8.4–8.5 GPM are designed to support several fixtures simultaneously.
How do I choose between natural gas and propane?
Natural gas is common for city utilities; propane is used where natural gas isn’t available. Check availability and piping requirements for your home.
Is a recirculation feature worth it?
Recirculation saves wait time for hot water, especially in larger homes or long runs of piping, but adds complexity and cost to the system.