A tankless water heater should run for many years, so the best rated models are the ones with a proven design, a long heat exchanger warranty and parts a plumber can service. We favored long-running product lines from established makers over flashy new features. These four have the track record and support to back them up.
We compared design history, warranty terms, serviceability, flow and efficiency using manufacturer specifications and long-term owner feedback. For our overall picks see the best tankless water heater guide; our Editorial Policy explains our process. Gas units require professional installation.
Top 3 Best Rated Tankless Water Heaters
Rinnai RE160eP Non-Condensing Outdoor Propane Tankless Water Heater
- 15-yr HX warranty
- Outdoor
- LED codes
Takagi T-H3S-OS-N Condensing Outdoor Natural Gas Tankless Water Heater
- 8 GPM
- Condensing
- Low NOx
Rheem RTEX-13 13kW 240V Electric Tankless Water Heater
- 13kW
- Copper elements
- Serviceable
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Best Rated Tankless Water Heaters Compared
| # | Product | Key Features | |
|---|---|---|---|
| 1 |  Rinnai RE160eP Non-Condensing Outdoor Propane Tankless Water Heater |
| Check Latest Price |
| 2 |  Takagi T-H3S-OS-N Condensing Outdoor Natural Gas Tankless Water Heater |
| Check Latest Price |
| 3 |  Rheem RTEX-13 13kW 240V Electric Tankless Water Heater |
| Check Latest Price |
| 4 |  Rheem RTG-70DVLP-3 7.0 GPM Propane Tankless Water Heater (Indoor) |
| Check Latest Price |
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1. Rinnai RE160eP Non-Condensing Outdoor Propane Tankless Water Heater
Best Rated Overall
- 15-year heat exchanger, 5-year labor and 1-year parts residential guarantee
- Up to 6.1 GPM, about 5 fixtures
- Outdoor install, no indoor venting
- LED screen shows service reminders and error codes
- Cleaner internal layout for easier service
- Propane version (natural gas sold separately)
- Wi-Fi needs the Control-R module
- Fuel: propane
- Flow: up to 6.1 GPM
- Model: REU-VE2125WD-US-P
Rinnai’s RE series is a long-running, widely serviced line, and the warranty terms reflect the maker’s confidence in it.
Error codes on the LED screen make troubleshooting faster for your installer.
Who the Rinnai RE160eP fits best
Propane homes in mild climates.
Who should skip the Rinnai RE160eP
Very cold climates where outdoor units need freeze care.
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2. Takagi T-H3S-OS-N Condensing Outdoor Natural Gas Tankless Water Heater
Best Rated Condensing
- Condensing high efficiency
- 8 GPM for whole-house use
- Computerized safety, no pilot light
- Meets SCAQMD Rule 1146.2 ultra-low NOx
- Outdoor model only
- Needs condensate handling
- Fuel: natural gas
- Flow: up to 8 GPM
- Model: T-H3S-OS-N
Takagi has a long record in tankless heating, and the H3 condensing design is known for steady performance.
Ultra-low NOx certification matters in strict air-quality areas.
Who the Takagi T-H3S-OS-N fits best
Natural gas homes with outdoor wall space.
Who should skip the Takagi T-H3S-OS-N
Indoor installs.
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3. Rheem RTEX-13 13kW 240V Electric Tankless Water Heater
Best Rated Electric
- 13kW with self-modulating control
- Copper immersion elements are field serviceable
- External digital thermostat with ±1° accuracy
- 99.8% energy efficient (per Rheem)
- About 3.2 GPM
- Needs a 54A circuit
- Power: 13kW, 240V
- Flow: up to about 3.2 GPM
- Model: RTEX-13
The RTEX-13 has been around for years and its replaceable elements extend its life.
It suits one bathroom or a small home in a warm climate.
Who the Rheem RTEX-13 fits best
Small homes and apartments.
Who should skip the Rheem RTEX-13
Multi-bathroom homes.
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4. Rheem RTG-70DVLP-3 7.0 GPM Propane Tankless Water Heater (Indoor)
Best Rated Propane Indoor
- 7.0 GPM at a 35°F rise
- 160,000 BTU for 2–3 showers
- UEF 0.82
- Direct vent indoor install
- Non-condensing
- Propane version only
- Fuel: propane
- Flow: 7.0 GPM
- Model: RTG-70DVLP-3
Rheem’s RTG series is a widely serviced line, so parts and installers are easy to find.
It is a solid indoor choice for propane homes.
Who the Rheem RTG 7.0 GPM LP fits best
Indoor propane installs.
Who should skip the Rheem RTG 7.0 GPM LP
Natural gas homes.
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What Makes a Tankless Water Heater Last
Heat exchanger warranty
Look for 10–15 years on the heat exchanger, the most expensive part.
Serviceability
Field-replaceable elements and error codes reduce repair costs.
Maintenance
Flush yearly in hard water areas and consider a scale filter.
| Model | Fuel | Why it lasts |
|---|---|---|
| Rinnai RE160eP | Propane | 15-yr HX warranty |
| Takagi T-H3S-OS-N | Natural gas | Proven condensing design |
| Rheem RTEX-13 | Electric | Replaceable copper elements |
| Rheem RTG 7.0 | Propane | Widely serviced line |
Frequently Asked Questions
What is the best rated tankless water heater?
The Rinnai RE160eP for its warranty and track record.
How long do tankless water heaters last?
Often 15–20 years with regular flushing.
Are electric models reliable?
Yes, and serviceable elements extend their life.
Does warranty require professional install?
Most gas warranties do; check the terms.
Final Verdict: Best Rated Tankless Water Heater
The Rinnai RE160eP is the best rated tankless water heater. The Takagi T-H3S-OS-N is the best rated condensing model, and the Rheem RTEX-13 is the best rated electric unit.
Overall: Rinnai RE160eP Non-Condensing Outdoor Propane Tankless Water Heater Check Latest Price
Condensing: Takagi T-H3S-OS-N Condensing Outdoor Natural Gas Tankless Water Heater Check Latest Price
Electric: Rheem RTEX-13 13kW 240V Electric Tankless Water Heater Check Latest Price
Choose a proven line and maintain it well.
Looking for something else? Browse all of our Water Heaters guides and the wider Heating & Cooling section.
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