The best outdoor tankless water heater depends on fuel type, household demand, and the number of fixtures used at once. The Rheem RTG is best for larger natural-gas homes, while the Ranein 8.5 GPM model offers the highest listed flow rate among these picks. For propane, consider the NOVIEEX or Ranein 5.3 GPM models. Westinghouse is a natural-gas option for buyers who prioritize its stated temperature stability.
| Product | Fuel | Listed Flow | Best For |
|---|---|---|---|
| Ranein 8.5 GPM | Natural gas | 8.5 GPM | Higher stated flow demand |
| Rheem RTG Series | Natural gas | 8.4 GPM | Large homes |
| NOVIEEX Outdoor | Propane | 5.3 GPM | Propane households |
| Ranein Propane 5.3 GPM | Propane | 5.3 GPM | Outdoor and patio setups |
| Westinghouse Outdoor | Natural gas | 8.1 GPM | Temperature stability |
Ranein Natural Gas 8.5 GPM
This Ranein model is best for buyers seeking a high stated flow rate in an outdoor natural-gas unit. It is rated at 8.5 GPM and 190,000 BTU, and its compact listed dimensions are 24.3 by 15.1 by 8.1 inches. The product description says its blower adjusts to external wind pressure and water-temperature changes to supply oxygen for combustion.
Choose this if you want on-demand hot water without waiting for a storage tank to preheat. Its standard 3/4-inch NPT water and gas connections are listed as installation features. A limitation is that the provided information does not specify a flow rate at a particular temperature rise, so compare the rating with your household’s actual demand and incoming water conditions.
Rheem RTG Series 8.4 GPM
The Rheem RTG is best for larger natural-gas homes that need hot water across multiple bathrooms. It provides a listed 8.4 GPM at a 35°F temperature rise, with 180,000 BTU per hour. The manufacturer listing says it can support three to four simultaneous showers and identifies it as a non-condensing, outdoor-installation model. Outdoor placement eliminates the need for venting, according to the product details.
Its stated 0.82 Uniform Energy Factor gives buyers an efficiency figure for comparison. Choose it if the 35°F-rise flow rating matches your expected use. The key limitation is that the 8.4 GPM figure is specified at that temperature rise; it should not be treated as a guaranteed flow rate under every water-temperature condition. The listing recommends wall mounting by a qualified installer.
Novieex Propane Outdoor 5.3 GPM
This NOVIEEX unit is best for homes using propane that need a mid-range listed flow rate. It is rated at 5.3 GPM and 120,000 BTU, and its product details describe hot-water service for multiple outlets. It has a powder-coated steel housing described as resistant to rust, corrosion, rain, and snow. The unit uses 3/4-inch NPT water connections and is listed for outdoor mounting without indoor venting.
Choose this model if propane is your required fuel and the listed capacity suits your household. One important limitation is its electrical requirement: the specifications list 110–120V AC at 60Hz. Confirm that the intended installation has the required power supply, as well as a compatible propane connection.
Ranein Propane 5.3 GPM Outdoor
The Ranein propane model is best for buyers looking for a compact outdoor unit with a listed 5.3 GPM capacity. It is rated at 130,000 BTU and measures 23.2 by 14.2 by 5.7 inches, according to the listing. Features include an LED control panel and anti-freeze protection, as stated in the product title. Its blower is described as adjusting to wind pressure and water-temperature changes.
Its listed 3/4-inch NPT water and gas connections can be useful when comparing installation requirements. Choose it if you want propane operation and a compact form. The supplied details do not state the temperature rise associated with its 5.3 GPM rating, so do not compare that figure as though all models were rated under identical conditions.
Westinghouse Natural Gas Outdoor
Westinghouse is best for natural-gas buyers who value the product’s stated temperature control. The listing gives a maximum flow of 8.1 GPM and 180,000 BTU, and says the unit can support three to five fixtures simultaneously. Its self-modulating technology is described as maintaining temperature within ±1°F by adjusting gas and water flow. The listing also identifies it as CSA certified.
Choose this model if its natural-gas fuel and stated capacity match your setup and you want the specified temperature-stability feature. A limitation is that the 8.1 GPM figure is presented as a maximum; the provided details do not give a specific temperature-rise condition for that rate.
Buying Guide: How To Choose An Outdoor Tankless Water Heater
Does the fuel type match your home?
Start with the available fuel. The Ranein 8.5 GPM, Rheem, and Westinghouse models are listed for natural gas. The NOVIEEX and smaller Ranein model use propane. Natural-gas and propane appliances are not interchangeable based on these listings, so select the fuel type specified for the unit.
How much flow do you need?
Compare the number of hot-water fixtures likely to run together with the product’s GPM rating. The 8.1–8.5 GPM options have higher stated maximum flow than the 5.3 GPM propane models. The Rheem listing provides a specific condition—8.4 GPM at a 35°F rise—while several other listings do not state the temperature-rise condition. Treat ratings carefully and compare like-for-like specifications where available.
What installation details should you verify?
Check the required gas and water connections, available electrical supply if applicable, mounting location, and local installation requirements before purchase. Outdoor units avoid indoor venting according to their listings, but they still require a suitable exterior location and correct utility connections. Have a qualified professional evaluate the installation when needed.
What matters in cold or exposed locations?
Review the specific product’s stated weather and freeze-related features. The Ranein propane listing mentions anti-freeze protection, while NOVIEEX describes a housing designed to resist outdoor exposure. Do not assume all outdoor models have identical freeze protection or weather resistance; confirm details for the exact unit and installation conditions.
Frequently Asked Questions
Are outdoor tankless water heaters vented indoors?
The Rheem listing says outdoor installation eliminates venting, and the NOVIEEX listing says no indoor venting is required. Follow the installation requirements for the selected model.
Can a propane model replace a natural-gas model?
These products are specified for one fuel type or the other. Choose a model listed for the fuel available at the installation site.
Does a higher GPM rating always mean better performance?
No. Flow ratings may be stated at different temperature-rise conditions. The Rheem, for example, specifies 8.4 GPM at a 35°F rise, while the other provided details do not consistently state a comparable condition.
Do outdoor tankless water heaters need electricity?
Electrical requirements depend on the model. NOVIEEX lists 110–120V AC at 60Hz. Check the specifications for any model under consideration before installation.