What Temperature Should Your Water Heater Be Set To?
The default factory setting is 140F but the DOE recommends 120F. Here is why the difference matters for safety and savings.
Safety Disclaimer
Water heater maintenance involves working with pressurized systems, scalding hot water, and potentially hazardous electrical or gas connections. Always shut off power (electric heaters) or gas supply (gas heaters) and allow water to cool to a safe temperature before beginning any maintenance. Wear appropriate safety equipment including gloves and eye protection. If you're uncomfortable with any step, contact a licensed plumber.
The Two Camps
120°F (Department of Energy Recommendation)
- Reduces risk of scalding (particularly important with children and elderly)
- Saves 6-10% on water heating energy costs
- Slows mineral buildup and corrosion in the tank and pipes
- Sufficient for most household tasks
140°F (Factory Default on Most Heaters)
- Kills Legionella bacteria more effectively
- Provides hotter water at the tap after heat loss through pipes
- Better for dishwashers without internal heating elements
- Required by some building codes for commercial properties
For more on this topic, see our guide on Water Heater Temperature Settings: Finding the Right Balance.
The Scalding Risk
Water at 140°F causes a third-degree burn in 5 seconds. Water at 120°F takes 5 minutes. This is a critical safety consideration for homes with young children, elderly residents, or anyone with reduced sensation.
For more on this topic, see our guide on Water Heater Safety: 7 Hazards Every Homeowner Should Know.
The Legionella Consideration
Legionella bacteria (which causes Legionnaires’ disease) can grow in water between 77-113°F. At 120°F, Legionella is inhibited but not killed. At 140°F, it is killed within minutes.
For most healthy households, the risk of Legionella at 120°F is extremely low. For immunocompromised individuals or large buildings with long pipe runs, 140°F with mixing valves at the point of use is the safer approach.
How to Check Your Current Setting
- Run hot water from the tap closest to the water heater for 2-3 minutes.
- Fill a glass and measure the temperature with a cooking thermometer.
- Compare to the thermostat setting on the heater.
How to Adjust
- Gas heaters: Turn the dial on the gas valve. Most have marked temperature positions.
- Electric heaters: Turn off the breaker. Remove the access panels. Use a flathead screwdriver to adjust the thermostat. Electric heaters typically have two thermostats (upper and lower); set both to the same temperature.
The Best Compromise
Set your water heater to 120°F and install an anti-scald mixing valve if you want extra protection. If you have a dishwasher without a booster heater, consider 125°F.