Tankless Water Heaters
Best Tankless Instant 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 whole-home hot water on demand, the MIZUDO leads this list with 10.3 GPM and 199,000 BTU, plus WiFi and app control. If you need gas flexibility, the Rinnai runs on natural gas or propane with up to 10 GPM, while the Westinghouse adds app and voice control at 7.9 GPM.
Starting out? See the main guide: Best Tankless Water Heater
Top picks at a glance
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Best OverallMIZUDO Natural Gas Tankless Water Heater9.8 View on Amazon -
9.7 View on Amazon -
9.4 View on Amazon -
Also GreatRheem RTG Series 8.4 GPM Natural Gas9.4 View on Amazon -
9.2 View on Amazon
Compare the specs
Ranked on flow rate, temperature control, phone app 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 | Phone app control | Weight | Warranty |
|---|---|---|---|---|---|---|
| 1. MIZUDO Natural Gas Tankless Water Heater | 10.3 GPM | natural gas | Yes | Yes | 55.5 lb | 2-year |
| 2. Rinnai RX180iN Condensing Smart Sense Tankless Water | 10 GPM | propane or natural gas | — | — | 54 lb | 5-year |
| 3. Westinghouse Tankless Water Heater Propane Indoor | 7.9 GPM | propane | Yes | Yes | — | — |
| 4. Rheem RTG Series 8.4 GPM Natural Gas | 8.4 GPM | natural gas | Yes | — | 39.25 lb | 1-year |
| 5. FOGATTI Tankless Water Heater Gas Propane Outdoor | 5.1 GPM | propane | Yes | — | 29.3 lb | 2-year |
MIZUDO Natural Gas Tankless Water Heater
It offers 10.3 GPM and 199,000 BTU with WiFi and app control, a 95°F to 149°F range, and 0.53 GPM low-flow activation.
- Flow rate: 10.3, the most here
- Fuel: natural gas
- Temperature control
- Phone app control
- 2-year warranty stated
Good for
- Buyers who want 10.3 GPM for a whole home with 5-7 outlets
- Buyers who want WiFi and app control with a 95°F to 149°F range
Skip it if
- You need more than 10.3 GPM of flow
- You live above 3,000 feet
It has WiFi and app control, an LED display, and a temperature range of 95°F to 149°F with a default 107°F daily comfort setting. Low-flow activation is 0.53 GPM. It measures 24.8 x 15.9 x 10.4 inches and weighs 55.5 lb. Warranty is 2 years for the full unit and 5 years for the heat exchanger.
Rinnai RX180iN Condensing Smart Sense Tankless Water
It provides up to 10 GPM for 6 fixtures at once, supports natural gas or propane, and installs indoors or outdoors.
- Flow rate: 10
- Fuel: propane or natural gas
- 5-year warranty stated
Good for
- Buyers who want a unit that runs on natural gas or propane
- Buyers who want indoor or outdoor installation with Versa Vent
Skip it if
- You need more than 10 GPM of flow
- You need a unit that runs on electricity only
It supports natural gas or propane through a Smart Sense gas control system and installs indoors or outdoors with Versa Vent. It provides up to 10 GPM and 6 fixtures at once, with a UEF of .98 and a Quick Flush feature. The interface is easy to use, and the Rinnai Central App helps with setup, service, and troubleshooting. Residential warranty covers the heat exchanger for 15 years, parts for 5 years, and labor for 5 years with registration within 90 days.
Westinghouse Tankless Water Heater Propane Indoor
It delivers up to 7.9 GPM and 180,000 BTU for 3-5 fixtures, with WiFi app and voice control and ±1°F stability.
- Flow rate: 7.9
- Fuel: propane
- Temperature control
- Phone app control
Good for
- Buyers who want a propane unit for 3-5 fixtures
- Buyers who want WiFi app and voice control
Skip it if
- You need more than 7.9 GPM of flow
- You need a natural gas or electric unit
It has WiFi app and voice control, ±1°F temperature stability, and a variable-speed combustion fan. It delivers up to 7.9 GPM and 180,000 BTU for 3-5 fixtures, with freeze protection and a copper heat exchanger. It uses 3/4-inch NPT residential plumbing connections.
Rheem RTG Series 8.4 GPM Natural Gas
It delivers 8.4 GPM at a 35°F temperature rise with 180,000 BTU/hr output for 3-4 simultaneous showers, plus freeze protection.
- Flow rate: 8.4
- Fuel: natural gas
- Temperature control
- 1-year warranty stated
Good for
- Buyers who want 8.4 GPM for 3-4 simultaneous showers
- Buyers who want a natural gas unit with a digital LED temperature panel
Skip it if
- You need more than 8.4 GPM of flow
- You need a propane or electric unit
It has a digital LED temperature control panel with ±1°F adjustments, freeze protection, and flame failure protection. It mounts on a wall and weighs 39.25 lb. Warranty is 1 year for labor, with a 15-year heat exchanger warranty and a 5-year parts warranty.
FOGATTI Tankless Water Heater Gas Propane Outdoor
It delivers 5.1 GPM and 120,000 BTU for 2-4 outlets at once, with ±1°F control and a remote control panel.
- Flow rate: 5.1
- Fuel: propane
- Temperature control
- 2-year warranty stated
Good for
- Buyers who want a propane unit for 2-4 outlets
- Buyers who want outdoor installation with a remote control panel
Skip it if
- You need more than 5.1 GPM of flow
- You live above 2,000 feet
It has a copper heat exchanger, a 304 stainless steel burner, and a remote control panel for indoor operation. It measures 26.2 x 17.1 x 7.1 inches and weighs 29.3 lb, with low water pressure compatibility from 15 to 150 PSI. Warranty is 2 years for the full unit and 5 years for the heat exchanger.
How to choose
Flow rate and simultaneous fixtures
Flow rate, measured in gallons per minute, sets how much hot water a unit can deliver at once. A higher flow rate supports more fixtures running at the same time. The MIZUDO offers 10.3 GPM, the Rinnai provides up to 10 GPM for 6 fixtures at once, the Rheem delivers 8.4 GPM for 3-4 simultaneous showers, the Westinghouse delivers 7.9 GPM for 3-5 fixtures, and the FOGATTI delivers 5.1 GPM for 2-4 outlets at once. Match the flow rate to the fixtures that will run together.
Fuel type and installation
Fuel type decides what supply a home uses. The MIZUDO and the Rheem run on natural gas, the Westinghouse and the FOGATTI run on propane, and the Rinnai runs on natural gas or propane. Professional installation is recommended for the MIZUDO and the Rinnai, so check the fuel supply and the installation route before choosing.
Temperature control and app control
Temperature control holds water at a set temperature instead of letting it swing. The MIZUDO, the Westinghouse and the FOGATTI hold temperature within ±1°F. The MIZUDO and the Westinghouse add WiFi and app control for adjusting temperature and checking status from a phone. The Rinnai Central App helps with setup, service, and troubleshooting, while WiFi control needs the Controlr module, which is not included.
FAQ
What flow rate do I need for a whole home?
Match the flow rate to the fixtures that will run together. The MIZUDO offers 10.3 GPM, the Rinnai provides up to 10 GPM for 6 fixtures at once, the Rheem delivers 8.4 GPM for 3-4 simultaneous showers, the Westinghouse delivers 7.9 GPM for 3-5 fixtures, and the FOGATTI delivers 5.1 GPM for 2-4 outlets at once.
Do these tankless water heaters run on natural gas, propane, or electricity?
The MIZUDO and the Rheem run on natural gas, the Westinghouse and the FOGATTI run on propane, and the Rinnai runs on natural gas or propane.
Which of these water heaters can I control with an app?
The MIZUDO and the Westinghouse have WiFi and app control for adjusting temperature and checking operating status. WiFi control for the Rinnai needs the Controlr module, which is not included.
What warranty do these tankless water heaters carry?
The MIZUDO warranty is 2 years for the full unit and 5 years for the heat exchanger, the Rinnai warranty covers the heat exchanger for 15 years, parts for 5 years, and labor for 5 years with registration within 90 days, the Rheem warranty is 1 year for labor, and FOGATTI warranty is 2 years for the unit and 5 years for the heat exchanger.
