Tankless Water Heaters
Best Indoor Propane Tankless Water Heater (2026): Top 5 by the Specs
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The APUS leads this list with 140,000 BTU and 6.8 GPM for 4–5 water points, plus a built-in booster pump and a 95–140°F range. Every pick here runs on propane and mounts indoors.
Starting out? See the main guide: Best Tankless Water Heater
Top picks at a glance
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Best OverallAPUS Propane Tankless Water Heater9.8 View on Amazon -
Highest Flow RateRanein Propane Gas Tankless Water Heater9.8 View on Amazon -
9.6 View on Amazon -
9.5 View on Amazon -
Also GreatRheem RTG Series 8.4 GPM Liquid Propane9.2 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. APUS Propane Tankless Water Heater | 6.8 GPM | propane | Yes | — | — |
| 2. Ranein Propane Gas Tankless Water Heater | 8.5 GPM | propane | — | — | 2-year |
| 3. Rinnai RX130iN Condensing Smart Sense Tankless Water | 7.1 GPM | propane or natural gas | — | — | — |
| 4. GEARPASS Propane Gas Tankless Water Heater | 6.3 GPM | propane | Yes | — | 2-year |
| 5. Rheem RTG Series 8.4 GPM Liquid Propane | 8.4 GPM | propane | Yes | — | — |
APUS Propane Tankless Water Heater
Its 140,000 BTU burner and 6.8 GPM cover 4–5 water points, with a built-in booster pump and 95–140°F temperature control.
- Flow rate: 6.8 GPM
- Fuel: propane
- Temperature control
Good for
- Whole-home buyers serving 4–5 water points
- Buyers who want a built-in booster pump
Skip it if
- You need more than 6.8 GPM of flow
- You run more than 5 water points at once
It uses a built-in booster pump and single-circulation technology for zero cold water wait time, with a UEF of 0.81. The LED display or Tuya app sets 95–140°F, and 8 protection systems are built in. It measures 21.26 by 13.58 by 7.09 inches with standard 1/2-inch NPT connections, and it carries a 2-year manufacturer warranty.
Ranein Propane Gas Tankless Water Heater
Its 190,000 BTU capacity and 8.5 GPM cover 4–6 outlet points.
- Flow rate: 8.5 GPM, the highest here
- Fuel: propane
- 2-year warranty stated
Good for
- Large homes running 4–6 outlet points at once
- Buyers who want 8.5 GPM of flow
Skip it if
- Your home sits above 2,000 feet in elevation
- You need a unit under 24 inches long
Its blower adjusts speed with wind pressure and water temperature, and the compact body measures 24.25 by 15.08 by 8.07 inches. Standard 3/4-inch G water inlet fittings speed installation, and tankless operation ends the 30-minute preheating wait of tank heaters. It carries a 2-year warranty, and the pressure relief valve drains remaining water in cold weather.
Rinnai RX130iN Condensing Smart Sense Tankless Water
Its 7.1 GPM serves 4 fixtures at once, with propane or natural gas operation and a UEF of .97.
- Flow rate: 7.1 GPM
- Fuel: propane or natural gas
Good for
- Buyers who want propane or natural gas flexibility
- Homes needing 4 fixtures at once
Skip it if
- You need more than 7.1 GPM of flow
- You want WiFi control included in the box
Its Versa Vent allows indoor or outdoor installation, and Smart Sense gas control accepts propane or natural gas. The compact body serves 4 fixtures at once, and Quick Flush simplifies flushing. WiFi control comes through a separate Controlr module, and the residential warranty covers the heat exchanger for 15 years.
GEARPASS Propane Gas Tankless Water Heater
Its 160,000 BTU and 6.3 GPM serve multiple outlets, with an LED touchscreen and 95–140°F control.
- Flow rate: 6.3 GPM
- Fuel: propane
- Temperature control
- 2-year warranty stated
Good for
- Households needing several outlets at once
- Buyers who want LED touchscreen control
Skip it if
- You need more than 6.3 GPM of flow
- You want a natural gas unit
Its oxygen-free copper heat exchanger and stainless steel housing support durable heat transfer, and on-demand operation heats water only when required. The LED display and smart touch panel set 95–140°F, and the operating water pressure range runs 2.9–116 PSI. It includes a 2.36-inch horizontal vent pipe with G 1/2-inch water and gas connections, backed by a 2-year warranty.
Rheem RTG Series 8.4 GPM Liquid Propane
Its 180,000 BTU output and 8.4 GPM serve 3–4 simultaneous showers, with ±1°F digital temperature control.
- Flow rate: 8.4 GPM
- Fuel: propane
- Temperature control
Good for
- Large households running 3–4 showers at once
- Buyers who want a 15-year heat exchanger warranty
Skip it if
- You need more than 8.4 GPM of flow
- You want a condensing unit
Its non-condensing design delivers 8.4 GPM at a 35°F temperature rise with a UEF of 0.82, and direct venting suits indoor installation. The digital LED panel adjusts temperature in ±1°F steps, and freeze protection and flame failure protection are built in. Mounting hardware and a detailed installation manual are included, with a 15-year heat exchanger warranty and 5-year parts warranty.
How to choose
Match flow rate to simultaneous use
Flow rate in GPM sets how many outlets run at once. The Ranein reaches 8.5 GPM for 4–6 outlet points, the Rheem gives 8.4 GPM for 3–4 simultaneous showers, and the Rinnai gives 7.1 GPM for 4 fixtures at once. The APUS gives 6.8 GPM for 4–5 water points, and the GEARPASS gives 6.3 GPM for multiple outlets. Count the showers and taps you run together, then pick a flow rate that covers that total.
BTU, UEF, and temperature control
BTU states heating capacity: the Ranein lists 190,000 BTU, the Rheem 180,000 BTU, the GEARPASS 160,000 BTU, the APUS 140,000 BTU, and the Rinnai 130k BTU. UEF states energy efficiency: the Rinnai lists .97, the Rheem 0.82, and the APUS 0.81. Temperature control matters for steady output: the APUS and GEARPASS set 95–140°F, and the Rheem adjusts in ±1°F steps.
Indoor venting and professional installation
Every pick here mounts indoors, and several need a vent path: the Rheem and GEARPASS use direct venting, and the GEARPASS includes a 2.36-inch horizontal vent pipe. The Rinnai needs an RX-OVC vent cap for outdoor installation, and professional installation is recommended for the Rinnai and required for the Rheem. Check venting, gas connections, and water pressure before ordering, and drain the unit if it sits unused in cold weather.
FAQ
What flow rate do I need for a whole home?
Count the outlets you run at once. The Ranein covers 4–6 outlet points at 8.5 GPM, the APUS covers 4–5 water points at 6.8 GPM, and the GEARPASS serves multiple outlets at 6.3 GPM.
Can one of these heaters run on natural gas?
The Rinnai runs on propane or natural gas through its Smart Sense gas control system. The other four picks are propane units: the APUS, Ranein, GEARPASS, and Rheem.
Do these heaters need professional installation?
Professional installation is required for the Rheem and recommended for the Rinnai. The GEARPASS offers professional customer support for installation and operation questions.
What temperature range can I set?
The APUS and GEARPASS set 95–140°F, and the Rheem adjusts in ±1°F steps on its LED panel. The Rinnai uses an easy-to-use interface for temperature control.
