The best temperature for a tankless water heater is typically set between 120°F to 140°F for optimal efficiency and safety.
Ever stepped into a scalding shower or waited forever for lukewarm water? Setting the wrong temperature on your tankless water heater can lead to energy waste, safety risks, or bacterial growth.
The right tankless water heater temperature can balance efficiency, comfort, and safety. In this guide, we’ll cover the ideal settings, safety tips, and adjustments for different needs. For advanced troubleshooting, check our water heater maintenance guide.
Key Takeaways
- 120°F (49°C) is the safest and most efficient default setting.
- Higher temperatures (130–140°F) may be needed for dishwashers or immunocompromised households.
- Lower temperatures risk bacterial growth (e.g., Legionella).
- Adjust settings seasonally for energy savings.
1. Why 120°F Is the Best Default Setting
The Consumer Product Safety Commission (CPSC) recommends 120°F for both tank and tankless water heaters. This temperature:
- Prevents scalding: Children and seniors can suffer burns in seconds at 140°F+.
- Saves energy: Each 10°F reduction lowers energy bills by 3–5% (U.S. Department of Energy).
- Balances safety and comfort: Ideal for showers, handwashing, and laundry.
Factory settings often default to 140°F, so always verify your unit’s temperature.
2. When to Use Higher Temperatures (130–140°F)
Exceptions to the 120°F rule include:
- Dishwashers without pre-heat cycles: 140°F ensures sanitization.
- Households with immunocompromised members: Higher temps kill bacteria like Legionella.
- Cold climates: Compensate for heat loss in pipes.
Warning: Install anti-scald devices if using 130°F+ to prevent burns.
3. Risks of Low Temperatures (Below 120°F)
While lower temps save energy, they pose health risks:
- Bacterial growth: Legionella thrives at 77–113°F (CDC).
- Inconsistent heating: Tankless units may struggle to meet demand.
4. How to Adjust Your Tankless Water Heater
Steps to change the temperature:
- Locate the control panel: Typically labeled with °F or letters (A/B/C).
- Use a thermometer: Test water at a faucet after adjustments.
- Consult the manual: Brands like Navien or Rinnai have model-specific steps.
5. Seasonal Adjustments for Efficiency
Optimize settings year-round:
- Winter: Increase by 5–10°F if incoming water is colder.
- Summer: Lower to 115–120°F to save energy.
Summary Table: Tankless Water Heater Temperatures
| Temperature | Best For | Risks |
|---|---|---|
| 120°F (49°C) | Most households | None |
| 130°F (54°C) | Dishwashers, cold climates | Scalding |
| 140°F (60°C) | Sanitization needs | High burn risk |
| <110°F (43°C) | Energy savings | Bacterial growth |
Final Words
Set your tankless water heater to 120°F for a balance of safety and efficiency. Adjust higher only for specific needs, and always prioritize anti-scald measures. For more tips, explore our energy-saving guide.
