Every tankless water heater needs some care, mostly flushing out mineral scale once a year in hard-water areas. The easiest heaters to maintain make that job quick, let a technician replace parts without swapping the whole unit, or keep water away from the heating element in the first place. These three are the lowest-upkeep tankless heaters we found.
We compared flushing features, serviceable parts, scale protection and diagnostics using manufacturer specifications and owner feedback. For filters that cut scale, see the best tankless water heater replacement filter guide; for service valves see the best tankless water heater accessories kit. Our Editorial Policy explains how we choose. Gas units need licensed installation and working CO alarms.
Top 3 Easy-Maintenance Tankless Water Heaters
Rinnai RX160iN Condensing Smart Sense Tankless Water Heater
- Quick Flush
- 9 GPM
- NG or LP
Rheem RTEX-18 18kW 240V Electric Tankless Water Heater
- Serviceable
- 18kW
- ±1°
ThermoMate ET080 8kW 240V Electric Tankless Water Heater
- Dry element
- 8kW
- Compact
As an Amazon Associate we earn from qualifying purchases.
Easy-Maintenance Tankless Water Heaters Compared
| # | Product | Key Features | |
|---|---|---|---|
| 1 |  Rinnai RX160iN Condensing Smart Sense Tankless Water Heater |
| Check Latest Price |
| 2 |  Rheem RTEX-18 18kW 240V Electric Tankless Water Heater |
| Check Latest Price |
| 3 |  ThermoMate ET080 8kW 240V Electric Tankless Water Heater |
| Check Latest Price |
As an Amazon Associate we earn from qualifying purchases.
1. Rinnai RX160iN Condensing Smart Sense Tankless Water Heater
Best Gas
- Quick Flush feature for easier descaling
- One model runs on natural gas or propane
- Versa Vent for indoor or outdoor install
- Optional Wi-Fi monitoring
- RX-OVC vent cap needed outdoors
- Gas install required
- Fuel: natural gas or propane
- Flow: up to 9 GPM
- Model: RX160iN
Rinnai built a Quick Flush feature into the RX160iN to simplify yearly descaling.
Its Smart Sense gas control lets one model run on either fuel.
Who the Rinnai RX160iN fits best
Gas homes with hard water.
Who should skip the Rinnai RX160iN
All-electric homes.
As an Amazon Associate we earn from qualifying purchases.
2. Rheem RTEX-18 18kW 240V Electric Tankless Water Heater
Best Electric
- Copper heating elements are field serviceable
- Threaded elements for easy replacement
- External thermostatic control, ±1°
- Bottom 3/4″ NPT connections
- Needs heavy wiring
- Up to 4.4 GPM
- Power: 18kW, 240V
- Flow: up to 4.4 GPM
- Model: RTEX-18
Rheem lets a technician swap an element instead of the whole heater.
Temperature holds within about one degree.
Who the Rheem RTEX-18 fits best
Electric homes.
Who should skip the Rheem RTEX-18
Small panels.
As an Amazon Associate we earn from qualifying purchases.
3. ThermoMate ET080 8kW 240V Electric Tankless Water Heater
Lowest Upkeep
- Heating element separated from water lines
- Cast aluminum, leak-proof chamber
- Self-modulating 8kW
- Supports up to 2 faucets
- Needs a 40A double-pole breaker
- Max 131°F
- Power: 8kW, 240V
- Flow: 1.56 GPM at 35°F rise
- Model: ET080
ThermoMate keeps water off the element, which helps against scale and corrosion.
It suits a bathroom or kitchen.
Who the ThermoMate ET080 fits best
Point-of-use installs.
Who should skip the ThermoMate ET080
Whole-home use.
As an Amazon Associate we earn from qualifying purchases.
Simple Maintenance Routine
- Flush gas and electric units yearly in hard water.
- Clean the inlet screen.
- Install isolation valves for easy flushing.
- Check error codes and vents.
Frequently Asked Questions
Which tankless water heater is easiest to maintain?
The Rinnai RX160iN for gas thanks to Quick Flush, and the Rheem RTEX-18 for electric.
How often should I flush a tankless heater?
Once a year in hard water.
Can I replace parts myself?
Leave electrical parts to a licensed pro.
Does a filter reduce maintenance?
A scale inhibitor can slow buildup.
Final Verdict: Best Tankless Water Heater Easy Maintenance
The Rinnai RX160iN is the easiest gas tankless water heater to maintain, the Rheem RTEX-18 is the best electric, and the ThermoMate ET080 has the lowest upkeep.
Gas: Rinnai RX160iN Condensing Smart Sense Tankless Water Heater Check Latest Price
Electric: Rheem RTEX-18 18kW 240V Electric Tankless Water Heater Check Latest Price
Lowest upkeep: ThermoMate ET080 8kW 240V Electric Tankless Water Heater Check Latest Price
A yearly flush keeps any tankless heater running well.
Looking for something else? Browse all of our Water Heaters guides and the wider Heating & Cooling section.
As an Amazon Associate we earn from qualifying purchases.
Write Your Review
No reviews yet. Be the first to share your experience!