Adjusting the temperature on an electric hot water heater takes about 10 minutes and requires only a screwdriver. The process involves turning off power at the breaker, removing one or two access panels on the front of the tank, and turning a dial. Most electric heaters leave the factory set to 120°F, but yours may have been changed by a previous homeowner or installer.
What Temperature to Choose
The U.S. Department of Energy recommends 120°F for most households. At that setting, a tank set to 140°F can waste $36 to $61 per year in standby heat losses alone, so lowering from 140°F to 120°F pays for itself immediately. The 120°F mark also dramatically reduces scalding risk: water at 140°F causes a serious burn in about 3 seconds, while water at 120°F takes roughly 10 minutes to cause the same injury.
There are two situations where you might go higher. If your dishwasher doesn’t have a built-in booster heater, it may need water between 130°F and 140°F for proper sanitization. And if anyone in your household has a suppressed immune system or chronic respiratory disease, 140°F reduces the already-small risk of Legionella bacteria, which can grow in tanks kept at lower temperatures. The CDC recommends storing hot water above 140°F and keeping circulating water above 120°F to control Legionella in larger systems, though for most residential users 120°F is considered safe.
Tools You’ll Need
- Phillips screwdriver or 1/4-inch nut driver to remove the access panel(s)
- Flat-blade screwdriver to turn the thermostat dial
- Kitchen thermometer to verify the output temperature afterward
Step-by-Step Adjustment
Turn Off Power
Go to your electrical panel and flip the breaker labeled for the water heater. It’s typically a double-pole 30-amp breaker. Do not skip this step. The thermostat sits directly next to live wiring carrying 240 volts, which is enough to be fatal. If your breakers aren’t labeled, flip off the ones that look like double-width switches until you confirm the heater has no power.
Remove the Access Panels
Most residential electric water heaters have two access panels on the front of the tank, one upper and one lower, each held in place by a couple of screws. Use your Phillips screwdriver or nut driver to remove them. Behind each panel you’ll find a layer of insulation, usually fiberglass or foam. Fold it out of the way to expose the thermostat and heating element beneath.
Locate the Thermostat Dial
The thermostat is a small rectangular device mounted against the tank wall. You’ll see a dial or a slotted adjustment screw with temperature markings. Some models label specific degree values (120, 130, 140). Others use vague labels like “warm,” “hot,” and “very hot,” or simply show hash marks. If yours doesn’t show exact temperatures, the midpoint is generally around 120°F.
Adjust the Temperature
Use your flat-blade screwdriver to turn the dial. Clockwise increases the temperature, counterclockwise decreases it. If you’re making a small change, move the dial one notch at a time rather than jumping to the opposite end of the scale. You can always fine-tune later after checking the output at a faucet.
Repeat for the Lower Thermostat
If your heater has two access panels, it has two thermostats, one controlling the upper heating element and one controlling the lower. You need to adjust both. Set them to the same temperature or within 5 degrees of each other. Setting them far apart causes problems: if the upper thermostat is much lower than the bottom, only the bottom element does all the work, which wears it out faster. If the upper is much higher, you’ll get inconsistent hot water. Setting both to the same value is the simplest and most reliable approach.
Reassemble and Restore Power
Tuck the insulation back into place over each thermostat, reattach the access panels, and flip the breaker back on. The water heater will now begin heating to your new setting. Give it one to two hours to reach the target temperature before testing.
How to Verify the New Temperature
Thermostat dials on electric water heaters are not precision instruments. The number on the dial is an approximation, so you should always check the actual output. After waiting at least an hour, turn on the hot water at the faucet closest to the water heater. Let it run for about a minute until it’s fully hot, then hold a kitchen thermometer under the stream. If the reading is more than a few degrees off from your target, go back and nudge the dial slightly in the appropriate direction, then recheck in another hour.
This test-and-adjust cycle is normal. It often takes two or three rounds to dial in the exact temperature you want, especially on heaters with unmarked dials.
The Red Reset Button
While you have the access panel open, you may notice a small red button near the upper thermostat. This is the high-limit switch, a safety device that cuts power to the heating elements if the water temperature reaches 180°F. If your heater suddenly stops producing hot water, a tripped reset button is a common cause. You can press it to restore power.
However, if it trips repeatedly, the thermostat itself is likely failing and allowing the water to overheat. A tripping reset button is not something to ignore or keep resetting. It means the safety mechanism is doing its job, and the thermostat probably needs replacement.
Why the Factory Setting Might Not Match
Even though most manufacturers ship heaters set to 120°F, the dial may have been turned up by a plumber during installation or by a previous homeowner who wanted hotter water. If you’ve moved into a new home and the water feels scalding, checking the thermostat is a good first step. It’s also worth adjusting seasonally: incoming cold water is colder in winter, so some people nudge the setting up 5 to 10 degrees during cold months to compensate, then bring it back down in summer to save energy.