Tankless Water Heaters
Best 50 Gallon Tankless Water Heater (2026): Top 5 by the Specs
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 a home replacing a 50-gallon tank, the Rheem RTG Series leads with 9.5 GPM at a 35°F temperature rise and 199,900 BTU/hr output for 3-4 simultaneous showers. The other four picks cover smaller simultaneous loads, from 4.42 GPM to 8.1 GPM, and all five run on natural gas with temperature control.
Starting out? See the main guide: Best Tankless Water Heater
Top picks at a glance
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Best OverallRheem RTG Series 9.5 GPM Natural Gas9.8 View on Amazon -
9.7 View on Amazon -
9.6 View on Amazon -
9.4 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. Rheem RTG Series 9.5 GPM Natural Gas | 9.5 GPM | Natural Gas | Yes | 46.5 lb | 1-year |
| 2. APUS Natural Gas Tankless Water Heater | 4.42 GPM | Natural Gas | Yes | 19.18 lb | 2-year |
| 3. ThermoMate CZ422NG Natural Gas Tankless Water Heater | 5 GPM | Natural Gas | Yes | 22 lb | 3-year |
| 4. FOGATTI Tankless Water Heater Natural Gas Outdoor | 8.1 GPM | Natural Gas | Yes | 43.2 lb | 2-year |
| 5. MIZUDO 120,000 BTU Natural Gas Tankless Water | 5.1 GPM | Natural Gas | Yes | — | 2-year |
Rheem RTG Series 9.5 GPM Natural Gas
It delivers 9.5 GPM at a 35°F temperature rise with 199,900 BTU/hr output for 3-4 simultaneous showers.
- Flow rate: 9.5 GPM, the highest here
- Fuel: Natural Gas
- Temperature control
- 1-year warranty stated
Good for
- Buyers replacing a 50-gallon tank heater with a wall-mount unit
- Homes running 3-4 water points at the same time
Skip it if
- You need a unit under 46.5 lb to move easily
- You want an outdoor installation instead of indoor
It has a digital LED temperature control panel with ±1°F adjustments, freeze protection and flame failure protection. The 0.82 UEF non-condensing unit uses a direct vent system for indoor installation. The box includes mounting hardware and a detailed installation manual.
APUS Natural Gas Tankless Water Heater
It supplies 4.42 GPM at 95,000 BTU for 2 showers plus 1 sink, with temperature control from 95°F to 140°F.
- Flow rate: 4.42 GPM
- Fuel: Natural Gas
- Temperature control
- 2-year warranty stated
Good for
- Buyers who want a low-flow start at 0.66 GPM
- Homes with 2 showers and 1 sink running together
Skip it if
- You need more than 4.42 GPM of flow
- You want a warranty longer than 2 years
It has an LED touchscreen and holds temperature within ±1°F of the setting, adjustable from 95°F to 140°F. The 0.66 GPM low-flow start technology suits small draws, and freeze protection activates at 41°F. It measures 20.55 inches high, 13.27 inches wide and 5.91 inches deep, and weighs 19.18 lb.
ThermoMate CZ422NG Natural Gas Tankless Water Heater
It delivers up to 5 GPM at 102,000 BTU for two showers at the same time, with a 3.5-inch LED display.
- Flow rate: 5 GPM
- Fuel: Natural Gas
- Temperature control
- 3-year warranty stated
Good for
- Buyers who want a 90°F to 140°F temperature range
- Homes running two showers at the same time
Skip it if
- You need more than 5 GPM of flow
- You want a warranty longer than 3 years
It adjusts temperature from 90°F to 140°F on a 3.5-inch LED display that also shows flow, fan and flame status. The unit measures 21 inches high, 13 inches wide and 7 inches deep, with standard 3/4-inch NPT water connections and a 3-inch OD vent connection. Freeze protection activates at 41°F, and it carries a 3-year warranty.
FOGATTI Tankless Water Heater Natural Gas Outdoor
It delivers up to 8.1 GPM at 180,000 BTU for 3-5 outlet points, built for outdoor installation with a remote control panel.
- Flow rate: 8.1 GPM
- Fuel: Natural Gas
- Temperature control
- 2-year warranty stated
Good for
- Buyers who want an outdoor unit with indoor control
- Homes running 3-5 outlet points at once
Skip it if
- You need an indoor-only installation
- You need a unit under 43.2 lb
It uses water servo technology and temperature sensors to hold temperature within ±1°F, with a four-stage combustion system. The unit measures 26.2 inches by 17.1 inches by 7.1 inches and works with water pressure from 15 to 150 PSI. It has an oxygen-free copper heat exchanger, a 304 stainless steel burner and CSA certification.
MIZUDO 120,000 BTU Natural Gas Tankless Water
It delivers 5.1 GPM at 120,000 BTU for 2-4 outlet points, with WiFi and app control for remote temperature changes.
- Flow rate: 5.1 GPM
- Fuel: Natural Gas
- Temperature control
- 2-year warranty stated
Good for
- Buyers who want WiFi and app control
- Homes needing indoor or outdoor installation flexibility
Skip it if
- You need more than 5.1 GPM of flow
- You want a warranty longer than 2 years
It manages temperature remotely through a dedicated mobile application, with settings, energy usage and maintenance notifications. The unit converts from indoor to outdoor use with accessory kits, and indoor installation uses a 3-inch OD vent pipe system. It has freeze protection, dry burn prevention, flame failure detection and exhaust blockage protection.
How to choose
Match flow rate to simultaneous use
Flow rate in gallons per minute decides how many showers and sinks can run at once. The Rheem delivers 9.5 GPM for 3-4 simultaneous showers, the FOGATTI delivers up to 8.1 GPM for 3-5 outlet points, and the APUS delivers 4.42 GPM for 2 showers plus 1 sink. Compare the flow rate against the number of fixtures your household runs together, not against the size of your old tank.
Temperature control and stability
A temperature control panel sets the output temperature, and a stability figure shows how close the unit holds it. The Rheem, APUS, ThermoMate and FOGATTI hold within ±1°F, and the MIZUDO holds within 1°F. The APUS adjusts from 95°F to 140°F, and the ThermoMate adjusts from 90°F to 140°F. The MIZUDO adds WiFi and app control for remote changes.
Indoor, outdoor and venting
Installation type narrows the list fast. The FOGATTI is built for outdoor installation with a remote control panel for indoor operation, while the Rheem, APUS and ThermoMate are indoor units. The MIZUDO converts between indoor and outdoor use with accessory kits, and its indoor installation uses a 3-inch OD vent pipe system. Check the vent connection and the installation type before choosing.
FAQ
What flow rate replaces a 50-gallon tank heater?
It depends on how many fixtures run at once. The Rheem delivers 9.5 GPM for 3-4 simultaneous showers, while the APUS delivers 4.42 GPM for 2 showers plus 1 sink.
Do these water heaters work on natural gas?
Yes, all five picks run on natural gas. The Rheem, APUS, ThermoMate, FOGATTI and MIZUDO are all natural gas tankless water heaters.
Can I control the temperature from my phone?
Only the MIZUDO offers WiFi and app control, with a dedicated mobile application for remote temperature settings.
Which pick is made for outdoor installation?
The FOGATTI is built for outdoor installation, with a remote control panel for indoor operation. The MIZUDO converts between indoor and outdoor use with accessory kits.
