Tip
The 120°F rule — fastest free water-heating savings
Most U.S. water heaters ship from the factory at 140°F. Lowering the setpoint to 120°F is the single fastest free water-heating savings move available — saves 4-15% on water heating cost per year, slows tank corrosion, reduces scalding risk for kids and elderly household members.
Why 120°F
- Hot enough for sanitation (Legionella does not multiply above 120°F)
- Comfortable shower temperature (no need to mix with cold)
- 4-15% less standby loss than 140°F
- Halves scalding-risk burns to children's skin
How to adjust
- Electric tank: turn off breaker first. Remove access panels (typically 2). Use a flat screwdriver to adjust both upper and lower thermostat dials. Replace covers, restore power.
- Gas tank: dial on front of unit. Mark current position; turn one notch down. Wait 24 hours; if water still hot enough, leave it.
- Heat pump water heater / smart tank: use the digital controls; set to 120°F directly.
- Tankless: use the remote controller; most factory-default to 120°F already.
When NOT to drop below 120°F
- Household members with weakened immune systems (Legionella concern)
- Dishwashers without internal heaters (need 130-140°F supply for proper sanitation)
- Homes with long pipe runs to fixtures (heat loss in pipes makes shower water lukewarm at the tap)