12 Tankless Propane Water Heater For Two Bathrooms Running At Same Time of 2026 Without Temperature Drops

1

Rheem RTG-84DVLP-3 High Efficiency Non-Condensing Indoor Tankless Liquid Propane Water

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  9.6
• Brand
  Rheem

Key specs2

Simultaneous Shower Capacity

8.4 GPM at 35°F rise (180,000 BTU)

Venting Architecture

Direct-vent system pulls fresh combustion air from outside and vents exhaust through dedicated indoor pipe runs, keeping indoor living spaces isolated from exhaust gases.

Pros & cons42

Pros

• 180,000 BTU burner and 8.4 GPM rating deliver sustained hot water across two bathrooms running at the same time
• Direct-vent indoor configuration allows quiet wall-mounted installation without outdoor exposure
• Digital LED display enables precise temperature adjustments within 1 degree
• Long-term manufacturer backing includes 15-year heat exchanger and 5-year parts warranty

Cons

• Non-condensing design requires dedicated direct venting through an exterior wall or roof
• Professional installation is required to mount the 46.5-pound cabinet and route gas lines

2

14L Tankless Water Heater Propane with Digital Display 3.66 GPM

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  8.9
• Brand
  Baococo

Key specs2

Portable Capacity

3.66 GPM (85,300 BTU)

Fixture Limitations

Engineered specifically for outdoor, camping, or single-fixture pet washing. It lacks the burner capacity required for concurrent whole-house bathroom usage.

Pros & cons32

Pros

• Lightweight 14-liter portable build carries easily for outdoor rinsing and camping setups
• Built-in digital display provides quick monitoring of working temperature
• Six integrated safety protections guard against dry combustion, flame failure, and freezing

Cons

• 85,300 BTU output and 3.66 GPM flow cannot supply two indoor residential showers at once
• Maximum water temperature tops out at 113°F under optimal inlet temperatures

3

FOGATTI Tankless Water Heater Gas Propane Indoor On Demand CSA

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  9.2
• Brand
  FOGATTI

Key specs2

Flow Modulation

Built-in water servo valve adjusts flow rates against incoming line pressure to prevent sudden cold shocks when a second bathroom tap opens.

Pressure Tolerance

15 to 150 PSI operating range

Pros & cons42

Pros

• 120,000 BTU output with 5.1 GPM capacity handles two modest shower fixtures simultaneously in moderate climates
• Water servo technology dynamically balances flow and gas intake to hold temperatures within 1 degree
• Compatible with lower household water pressures down to 15 PSI
• Durable construction features a copper heat exchanger and 304 stainless steel burner

Cons

• 5.1 GPM maximum flow will drop noticeably when incoming groundwater is near freezing
• Requires standard 120V AC electrical power to run internal sensors and controls

4

Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water

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  8.7
• Brand
  Rheem

Key specs2

Exterior Mounting Advantage

Mounting on an exterior wall frees up indoor utility space and eliminates the cost and complexity of drilling interior vent penetrations.

Heating Output

7.0 GPM at 35°F rise (160,000 BTU)

Pros & cons42

Pros

• 160,000 BTU burner and 7.0 GPM flow easily support two simultaneous showers without flow restriction
• Outdoor installation design completely eliminates indoor venting and flue piping requirements
• Heavy-duty metal cabinet includes built-in freeze protection for exterior wall mounting
• Digital LED controller maintains steady hot water temperature within 1 degree

Cons

• Outdoor-only installation requires a suitable exterior wall location and exterior plumbing runs
• Demands professional installation to verify gas supply pressure and outdoor code compliance

5

APUS Tankless Water Heater Propane Gas, Up to 4.42 GPM,

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  8.9
• Brand
  APUS

Key specs2

Acoustic Rating

36 dB operating sound level

Low Flow Ignition

0.66 GPM minimum start rate

Pros & cons42

Pros

• Ultra-compact 5.9-inch deep profile fits tightly into small utility closets or laundry rooms
• Low 0.66 GPM ignition activation ensures the burner fires up even for low-flow faucets
• Operates at a quiet 36 dB sound level during active combustion
• Smart CPU temperature management maintains output within 1 degree across 95°F to 140°F

Cons

• 95,000 BTU heating capacity struggles to support two full showers at once in cold winter climates
• Requires manual draining if ambient temperatures drop below 41°F during extended periods of disuse

6

GASLAND Gasmart C Propane Gas Tankless Water Heater Indoor, Max

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  7.8
• Brand
  GASLAND

Key specs2

Vent Kit Inclusions

Includes a dedicated 3-inch diameter exhaust pipe in the box, removing the guesswork of sourcing matched indoor venting components.

Plumbing Interface

3/4-inch NPT water connections

Pros & cons42

Pros

• 113,000 BTU burner and 5.0 GPM delivery provide adequate flow for two standard low-flow showerheads
• Product packaging includes the required 3-inch exhaust pipe for simplified indoor venting
• Standard 3/4-inch NPT water connections match typical residential plumbing lines
• Smart modulation chip continuously adjusts heating output to maintain water within 1 degree

Cons

• Ground temperatures in northern winter regions will restrict the realistic flow rate below 5 GPM
• Electrical power must stay continuously connected to operate internal freeze protection below 41°F

7

VEVOR Propane Tankless Water Heater, 4.3Gal Indoor 100000 BTU Instant

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  8.9
• Brand
  VEVOR

Key specs2

Fitting Diameter

1/2-inch NPT water connections

Control Interface

Front touch display provides instant status readouts and direct adjustments to help maintain consistent output within 1 degree.

Pros & cons42

Pros

• 100,000 BTU heating capacity delivers up to 4.3 GPM for single-bathroom homes or split usage
• Integrated vent outlet simplifies connection to standard direct-vent indoor flue runs
• Large LED touch panel shows real-time operating temperature and status clearly
• Internal smart sensors regulate gas burning to keep temperature within 1 degree

Cons

• Uses 1/2-inch NPT connectors which can bottleneck flow compared to standard 3/4-inch whole-house plumbing
• 4.3 GPM maximum output will not sustain two concurrent showers during colder months

8

MIZUDO 180,000 BTU Propane Tankless Water Heater,Outdoor,Max 8.1 GPM

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  7.4
• Brand
  MIZUDO

Key specs2

Concurrent Flow Capacity

8.1 GPM maximum flow (180,000 BTU)

High Elevation Limit

Rated for installations up to 2,000 feet

Pros & cons42

Pros

• Robust 180,000 BTU burner easily supports 8.1 GPM, feeding two to three bathrooms running at the same time
• Rapid heating system reaches set temperatures in 13 seconds with 1-degree precision
• Outdoor CSA certification eliminates indoor exhaust flues and venting hardware costs
• Wide temperature range adjustable up to 167°F accommodates high-temperature soaking tubs and appliances

Cons

• Not recommended by the manufacturer for high-altitude installations above 2,000 feet
• Residual water must be manually drained using the pressure relief valve during extended freezes

9

MIZUDO Propane Gas Tankless Water Heater, 199,000 BTU, Indoor

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  7.6
• Brand
  MIZUDO

Key specs2

Whole Home Throughput

10.3 GPM maximum flow (199,000 BTU)

Smart Connectivity

App and Alexa integration allow homeowners to fine-tune water temperature and receive abnormal status alerts without walking to the utility room.

Pros & cons42

Pros

• Heavy-duty 199,000 BTU input delivers up to 10.3 GPM, keeping multiple showers hot even in harsh winter weather
• Smart WiFi and Alexa connectivity allow remote temperature adjustments and operating alerts from your smartphone
• Low 0.53 GPM activation threshold prevents heater shutdown when running a single low-flow bathroom faucet
• Advanced gas modulation holds water temperature within 1 degree up to 149°F

Cons

• 55.5-pound indoor unit requires substantial wall reinforcement and dedicated venting
• Manufacturer specifies maximum operating altitude should not exceed 3,000 feet

10

18L Tankless Water Heater Propane with Digital Display 4.76 GPM

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  7.4
• Brand
  Baococo

Key specs2

Portable Heating Output

4.76 GPM (115,425 BTU)

Application Scope

Designed for RVs, camping cabins, and outdoor washing. It lacks the indoor flue and permanent plumbing ratings required for whole-home dual bathroom distribution.

Pros & cons32

Pros

• Generates 115,425 BTU heating output for portable use with up to 4.76 GPM water flow
• Portable exterior design includes an included shower head with a water-saving shut-off button
• Six safety protections include anti-freeze, flame failure shut-off, and high pressure relief

Cons

• Unvented portable design is restricted to outdoor and RV use, not permanent indoor living spaces
• Maximum water temperature is limited to 113°F, leaving narrow margin for high temperature rise

11

Ranein Propane Gas Tankless Water Heater, 5.3 GPM, 130,000 BTU,

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  7.3
• Brand
  Ranein

Key specs2

Combustion Blower Design

Positioning the combustion fan underneath prevents flue gas backdraft in outdoor wind conditions while adjusting airflow dynamically to water demand.

Inlet Sizing

3/4-inch NPT gas and water connections

Pros & cons42

Pros

• 130,000 BTU burner and 5.3 GPM flow easily handle two concurrent showers in moderate climates
• Bottom-mounted blower fan adjusts speed dynamically against outdoor wind pressure to prevent backflow
• Full 3/4-inch NPT fittings on both water and gas inlets ensure unrestricted flow without line restriction
• Outdoor installation eliminates the need to route indoor vent flues through interior walls

Cons

• Manufacturer does not recommend operation in locations with elevations over 2,000 feet
• Requires manual draining via the pressure relief valve during extended freezes when idle

12

Tankless Water Heater Instant Propane Gas Water Heater 14L 3.66GPM

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  7.1
• Brand
  Baococo

Key specs2

Minimum Operating Pressure

3.6 PSI startup pressure

Outdoor Utility Focus

Built for temporary recreational setups, off-grid cabins, and pet rinsing rather than permanent multi-shower residential hot water loops.

Pros & cons42

Pros

• Low-pressure ignition operates reliably on water pressure starting as low as 3.6 PSI
• Compact 11.4-inch square chassis stores easily in vehicles or outdoor gear sheds
• 85,300 BTU output provides continuous hot water for outdoor showers and vehicle washing
• Includes six safety protections including flameout, dry combustion, and low-flow lockout

Cons

• 3.66 GPM flow rate is insufficient to supply two residential bathrooms running simultaneously
• Portable open-burner architecture is strictly rated for outdoor operation

Last update on 2026-10-11 / Affiliate links / Images, Product Titles, and Product Highlights from Amazon Product Advertising API

How many GPM and BTU are needed to run two bathrooms at the same time?

You need a propane tankless unit delivering at least 7.0 to 10.3 GPM with a burner output between 160,000 and 199,000 BTU to comfortably supply two bathrooms at once. High-capacity models with 180,000 to 199,000 BTU can produce 8.1 to 10.3 GPM, which supports simultaneous demand across two to three bathrooms and kitchen faucets. Mid-range units rated at 7.0 to 8.4 GPM at a 35°F temperature rise generate 160,000 to 180,000 BTU of heating power. Systems delivering only 4.42 to 5.0 GPM with 95,000 to 113,000 BTU will struggle if two showers run concurrently, frequently forcing one or both to drop flow or lose heat.

Will a 5.0 GPM propane tankless water heater handle two showers in winter?

It depends entirely on your incoming groundwater temperature. A 5.0 GPM heater backed by 113,000 BTU provides whole-home hot water under moderate conditions, but cold winter water requires a much higher temperature rise to reach a comfortable shower. When incoming water drops to near freezing, the unit must slow down its flow through the heat exchanger to maintain heat, often falling well below 5.0 GPM. If your winter groundwater is particularly cold, paired high-demand fixtures will overwhelm a 5.0 GPM system. In setups where a central heater struggles with distant fixtures, adding a dedicated instant hot water heater near a secondary bathroom can balance the demand.

How does gas modulation prevent sudden shower temperature drops?

Advanced gas modulation continuously adjusts the burner flame in real time to keep water temperature within plus or minus 1°F of your setting. Units with smart CPU processing and dual inlet and outlet thermistors detect flow fluctuations immediately, preventing the shock of cold or scalding water when someone opens a second faucet. Certain high-output systems can respond and heat incoming flow in as little as 13 seconds. Without responsive gas modulation, opening a second shower valve dilutes hot water pressure and creates a noticeable temperature drop for the first bather.

Can a portable 3.66 GPM propane water heater run two bathrooms?

No. Portable 3.66 GPM propane units produce around 85,300 BTU per hour and are designed for camping, outdoor cabins, or single portable fixtures. They do not have the heating capacity or flow volume required to handle the simultaneous demands of two residential bathrooms. Attempting to route two active showers through an 85,300 BTU portable heater will leave both showers with weak pressure, lukewarm water, or an outright temperature crash.

Should I choose an indoor direct-vent heater or an outdoor propane model?

Your choice depends on your home layout and venting capabilities. Indoor propane models require dedicated venting, such as a 3-inch exhaust pipe, to discharge combustion exhaust safely through an exterior wall or roof. Outdoor propane heaters are built for exterior wall mounting and exhaust directly into the open air without indoor flue pipes. Many outdoor units feature blowers mounted underneath to prevent smoke backflow while saving interior square footage. Always verify your installation clearance, comparing the heater dimensions (such as 15.5 by 15.5 by 23.9 inches) against your intended wall or utility space.

What safety features protect propane tankless heaters from freezing or overheating?

Whole-house propane units rely on built-in freeze protection, overheat cutoff fuses, and thermistors to keep operation safe. Inlet and outlet thermistors continuously monitor water heat levels as water passes through the burner, keeping temperature safely capped up to 149°F. An overheat cutoff fuse shuts down the burner instantly if heat exchanger temperatures exceed safe operational limits. If your heater will be installed in an unconditioned indoor space or an exterior wall, verify that it carries CSA certification and standard freeze protection built directly into the chassis.