Tankless Water Heaters
Best Outdoor Tankless Water Heater (2026): Our 5 Picks Ranked
As an Amazon Associate I earn from qualifying purchases. Specs below come from each product's Amazon listing; we do not test products in person.
For an outdoor tankless water heater, the Ranein leads this list: a natural gas heater with 190,000 BTU and 8.5 GPM for 4 to 6 outlet points, with anti-freeze protection. The Rheem gives 8.4 GPM for 3 to 4 simultaneous showers, and the Westinghouse and FOGATTI cover 2 to 4 fixtures or outlets.
Starting out? See the main guide: Best Tankless Water Heater
Top picks at a glance
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Best OverallRanein Natural Gas Tankless Water Heater9.8 View on Amazon -
Runner-UpRheem RTG Series 8.4 GPM Natural Gas9.6 View on Amazon -
9.6 View on Amazon -
9.5 View on Amazon -
9.2 View on Amazon
Compare the specs
Ranked on flow rate, temperature control from each listing, plus how many buyers have rated it. A dash (—) means we could not confirm that figure from the listing.
| Pick | Flow rate | Fuel | Temperature control | Weight | Warranty |
|---|---|---|---|---|---|
| 1. Ranein Natural Gas Tankless Water Heater | 8.5 GPM | Natural Gas | — | 44 lb | — |
| 2. Rheem RTG Series 8.4 GPM Natural Gas | 8.4 GPM | Natural Gas | Yes | 39.25 lb | 1-year |
| 3. Westinghouse 120,000 BTU Natural Gas Tankless Water | 5.1 GPM | Natural Gas | Yes | — | — |
| 4. FOGATTI Tankless Water Heater Gas Propane Outdoor | 5.1 GPM | Propane | Yes | 29.3 lb | 2-year |
| 5. Rinnai V53DeP Propane Tankless Water Heater | 5.3 GPM | Propane | — | 33 lb | — |
Ranein Natural Gas Tankless Water Heater
It pairs 190,000 BTU natural gas heating with 8.5 GPM max flow for 4 to 6 outlet points.
- Flow rate: 8.5 GPM, the highest here
- Fuel: Natural Gas
Good for
- Owners of homes with 4 to 6 outlet points
- Buyers who want anti-freeze protection outdoors
Skip it if
- You need more than 8.5 GPM of flow
- You live above 2,000 feet
It uses standard 3/4-inch G water inlet fittings and gas inlets, in a 24.3 by 15.1 by 8.1 inch case. The blower adjusts speed with external wind pressure and water temperature, and anti-freeze protection prevents freezing and cracking inside. It weighs 44 lb.
Rheem RTG Series 8.4 GPM Natural Gas
It pairs 180,000 BTU per hour output with 8.4 GPM for 3 to 4 simultaneous showers and a 0.82 UEF.
- Flow rate: 8.4 GPM
- Fuel: Natural Gas
- Temperature control
- 1-year warranty stated
Good for
- Owners of multi-bathroom homes with 3 to 4 showers
- Buyers who want digital LED temperature control with ±1°F adjustments
Skip it if
- You need more than 8.4 GPM of flow
- You run more than 4 showers at once
It gives 8.4 GPM at a 35°F temperature rise with a durable metal cabinet for outdoor installation, which eliminates venting. The digital LED panel adjusts temperature with ±1°F precision, and freeze protection and flame failure protection are built in. Mounting hardware and an installation manual are included.
Westinghouse 120,000 BTU Natural Gas Tankless Water
It pairs 120,000 BTU natural gas heating with 5.1 GPM for 2 to 4 fixtures and ±1°F stability.
- Flow rate: 5.1 GPM
- Fuel: Natural Gas
- Temperature control
Good for
- Owners who run 2 to 4 fixtures at once
- Buyers who want a wall-mounted outdoor heater
Skip it if
- You need more than 5.1 GPM of flow
- You run more than 4 fixtures at once
It heats water only when needed, helping reduce standby energy loss, with self-modulating technology holding temperature within ±1°F. Freeze protection and a variable-speed combustion fan are built in, and it fits standard 3/4-inch NPT plumbing. Fully drain the system below 5°F or during extended non-use.
FOGATTI Tankless Water Heater Gas Propane Outdoor
It pairs 120,000 BTU propane heating with 5.1 GPM for 2 to 4 outlets and a remote control panel.
- Flow rate: 5.1 GPM
- Fuel: Propane
- Temperature control
- 2-year warranty stated
Good for
- Owners who run 2 to 4 outlets at once
- Buyers who want propane heating with indoor remote control
Skip it if
- You need more than 5.1 GPM of flow
- You run more than 4 outlets at once
It uses a copper heat exchanger with a 304 stainless steel burner and four-stage combustion, holding temperature within ±1°F. It measures 26.2 by 17.1 by 7.1 inches, works with low water pressures from 15 to 150 PSI, and comes with 2 years of full unit coverage and 5 years of heat exchanger coverage.
Rinnai V53DeP Propane Tankless Water Heater
It pairs propane heating with 5.3 GPM for multiple appliances in a compact outdoor design.
- Flow rate: 5.3 GPM
- Fuel: Propane
Good for
- Owners who want a compact heater for tight spaces
- Buyers who want propane heating on demand
Skip it if
- You need more than 5.3 GPM of flow
- You need a heater under 33 lb
It heats water on demand with scale detection features, in a compact outdoor design for tight spaces. Professional installation by a qualified technician is recommended. It weighs 33 lb.
How to choose
Match flow to simultaneous use
Flow rate sets how many outlets run at once. The Ranein gives 8.5 GPM for 4 to 6 outlet points, the Rheem gives 8.4 GPM for 3 to 4 simultaneous showers, and the Westinghouse and FOGATTI give 5.1 GPM for 2 to 4 fixtures or outlets, and the Rinnai gives 5.3 GPM. Count the showers and fixtures you run together, then pick a flow figure that covers them.
Fuel, venting and outdoor placement
Fuel differs across this list: the Ranein and Rheem use natural gas, and the Westinghouse uses natural gas while the FOGATTI and Rinnai use propane. Outdoor installation eliminates venting for the Rheem, and the Ranein blower adjusts speed with wind pressure. Check the fuel type and the venting needs of the pick you choose against your setup.
Freeze protection and draining
Outdoor heaters face freezing weather, so freeze protection matters. The Ranein, Rheem and Westinghouse include freeze protection, and the FOGATTI has an active heating anti-freeze device. The Westinghouse and FOGATTI instructions call for draining below 5°F or during extended non-use. Check the freeze and draining notes of the pick you choose.
FAQ
What flow rates do these heaters give?
The Ranein gives 8.5 GPM, the Rheem gives 8.4 GPM, the Rinnai gives 5.3 GPM, and the Westinghouse and FOGATTI give 5.1 GPM.
Which of these heaters use propane?
The FOGATTI and Rinnai use propane. The Ranein, Rheem and Westinghouse use natural gas.
Do these heaters need professional installation?
The Rinnai recommends professional installation by a qualified technician, and the Rheem supports wall mounting by a qualified installer. Check the installation note on each product before ordering.
Which heater here has a remote control panel?
The FOGATTI has a remote control panel for indoor operation, and its temperature sensors hold temperature within ±1°F.
