Set the water heater to 120°F and check it at the tap

Set the water heater so a thermometer at the hot tap reads 120°F. DOE's 2022 Energy Saver guide calls 120°F "a temperature considered safe for most of the population", and EPA's pollution prevention tips say turning the heater down to 120°F cuts water heating costs by 6 to 10 percent. The one condition is the dishwasher: the same DOE guide gives the go-ahead for 120°F when the dishwasher has an internal heating element that boosts water temperature, so check its manual first. Measuring and turning the dial is free, and renters and owners can both do it wherever they can reach the heater.

120°F is the setting DOE and CPSC both name

CPSC reaches 120°F from the scald side. CPSC's sheet on avoiding tap water scalds urges all users to lower their water heaters to 120°F, says most tap water scald injuries and deaths happen to older adults and children under five, and adds that the lower setting conserves energy and saves money.

The same CPSC sheet says most adults suffer third-degree burns after two seconds in 150°F water, that burns also occur after six seconds at 140°F or thirty seconds at 130°F, and that even at 120°F a five-minute exposure could result in third-degree burns. It tells you to hand-test bath water every time, especially for infants and young children. The dial does not replace that habit.

Check the dishwasher before you turn anything. DOE's 2022 guide says that, in general, if your dishwasher has an internal heating element that boosts water temperature, you can set your water heater to 120°F, and that ENERGY STAR certified dishwashers boost water to 140°F. Look in the dishwasher's manual for a booster heater. If it has none, check what the manual asks of the incoming water before you lower the heater.

EPA says turning it down cuts water heating costs 6 to 10 percent

Water heating is the second largest energy expense in a home and typically accounts for about 18% of energy usage, according to DOE's Energy Saver guide (2022). The same guide lists turning down the thermostat on the water heater as one of four primary ways to cut water heating bills. EPA puts the cut from turning the heater down to 120°F at 6 to 10 percent of water heating costs. The change itself is free.

Example, with published figures and one assumption. Georgia homes that heat water with electricity used an average of 3,263 kWh a year for it in 2020, according to EIA's RECS 2020 table CE4.6.EL.ST. Georgia's average residential price was 16.27 cents per kWh in July 2026, the latest month in EIA's Electric Power Monthly, Table 5.6.A (preliminary). Priced at July 2026's rate, 3,263 kWh × 16.27 cents = $530.89 a year, the kWh-times-rate arithmetic used to price any appliance. EPA's tip does not name a starting setting, so the example assumes a tap reading above 120°F before the change. Then 6% of $530.89 is $31.85 and 10% is $53.09: $31.85 to $53.09 a year.

DOE's 2022 guide names using less hot water as another of its four ways, and washing laundry in cold water is the free place to start.

Measure at the hot tap before and after you turn the dial

Use a candy or meat thermometer, the tool CPSC's scald sheet names. Hold it under the hot faucet first thing in the morning, or at least two hours after anyone used hot water. Write the reading down. If the reading is above 120°F, adjust the heater's thermostat following the manufacturer's instructions, then check again with the thermometer. Recheck the next morning, before the first shower, so the timing matches. In an apartment, CPSC says to contact the building manager about lowering the tap water temperature.

On an electric tank, the same CPSC sheet says most heaters have two thermostats behind upper and lower access panels, and both must be set to a common temperature. CPSC says the power comes off at the circuit breaker first and that hot water should not be used for at least two hours before setting. Some electric companies adjust it at no charge, CPSC notes; otherwise a licensed plumber does it.

On a gas tank, CPSC says thermostats differ and tells you to call your local gas company for instructions. Set the dial only as the heater's manual shows. Burner, gas line, venting and relief-valve work belongs to a licensed plumber or gas fitter, and sealing a home with gas appliances covers the carbon-monoxide alarms and the yearly inspection.