Most electric water heaters ship from the factory set to 120°F, but the thermostat is hidden behind an access panel, so there’s no obvious way to check or change it. Adjusting the temperature takes about 10 minutes, a couple of screwdrivers, and one important safety step: cutting the power first. Here’s how to do it.
What You’ll Need
Gather these before you start:
- Phillips screwdriver or 1/4-inch nut driver to remove the access panel(s)
- Flat-blade screwdriver to turn the thermostat dial
- Non-contact circuit tester to confirm the power is off
- Thermometer (a kitchen meat thermometer works fine) to verify the water temperature at the tap afterward
Step-by-Step: Adjusting the Thermostat
Start at your home’s electrical panel. Find the breaker labeled for the water heater and flip it to the OFF position. Then go back to the water heater and use a non-contact circuit tester on the wiring inside the junction box on top of the unit to confirm there’s no live current. This is not optional. Electric water heaters run on 240 volts, enough to cause serious injury.
Once you’ve confirmed the power is off, locate the access panel on the front of the tank. Most electric water heaters have two panels, an upper and a lower, each covering its own thermostat and heating element. Remove the screws with your Phillips screwdriver or nut driver and set the cover aside.
Behind the panel you’ll find a layer of insulation. Fold it out of the way. Underneath that is a plastic safety cover. Either pop it off or bend it upward to reveal the thermostat dial.
The dial has temperature markings and a small slot for a flat-blade screwdriver. Turn the slot to line up with your desired temperature. If your heater has two thermostats, set both to the same temperature. This keeps the upper and lower heating elements working in coordination so you get consistent hot water.
Replace the plastic safety cover, press the insulation back into place, and screw the access panels back on. Go back to your breaker panel and flip the circuit back to ON. The water heater will need time to reach the new setting, typically one to two hours for a noticeable change.
How to Verify the Actual Temperature
The thermostat dial is a rough guide, not a precision instrument. The only reliable way to know your water temperature is to measure it at the tap. Go to the faucet furthest from the water heater in your home and run the hot water for a full minute. Fill a glass and drop in a meat thermometer. That reading is your actual delivery temperature.
If it’s not where you want it, go back and nudge the thermostat dial in small increments. You don’t need large adjustments. A small turn changes the output by several degrees. Wait an hour or two between adjustments and retest at the same faucet.
What Temperature to Choose
120°F is the sweet spot for most households. It’s hot enough for comfortable showers, effective dishwashing, and laundry, while keeping energy costs and scalding risk lower. The U.S. Department of Energy recommends this setting, and it’s where most manufacturers set the thermostat before shipping.
The tradeoff with going lower is bacterial growth. Legionella, the bacteria responsible for Legionnaires’ disease, thrives between 77°F and 113°F and can still survive below 120°F. At 120°F, the CDC considers the risk very low for most people. Households with immunocompromised members or older adults sometimes keep the tank at 130°F or higher as an extra precaution. If you store water above 140°F, installing a mixing valve at the tap is the standard way to prevent scalding while keeping the tank hot enough to kill bacteria.
Why Scalding Risk Matters
Hot water burns happen faster than most people expect. According to the American Burn Association, water at 140°F causes a third-degree burn in just 5 seconds. At 148°F, it takes 2 seconds. At 155°F, a single second of contact is enough. Even at 133°F, a third-degree burn develops in 15 seconds, which is well within the time a young child or elderly person might be unable to move away.
At 120°F, it takes about 5 minutes of sustained contact to cause that level of burn. That margin of safety is the main reason 120°F is the standard recommendation, especially in homes with children or anyone with reduced sensation in their hands or feet.
Energy Savings From Lowering the Temperature
Your water heater is one of the biggest energy consumers in your home, typically accounting for about 15 to 20 percent of your utility bill. Every degree you lower the thermostat reduces the energy needed to keep that tank of water hot around the clock. Dropping from 140°F to 120°F produces a meaningful reduction in your monthly bill, and the adjustment takes minutes. If your water feels hot enough at a lower setting, there’s no reason to keep it higher.
Troubleshooting Common Issues
If you adjust both thermostats to the same setting but your hot water runs out quickly, the lower heating element or thermostat may be failing. The upper element heats the top of the tank first for quick recovery, while the lower element maintains the full tank. When only the upper element works, you get a small amount of very hot water followed by cold.
If the water never reaches the temperature you set, check that both thermostats are actually at the same reading. On some models, the markings are small and easy to misread. A mismatched pair, where one thermostat is set much lower than the other, will produce lukewarm water that never quite gets hot enough. If both dials match and the output is still low, the heating elements themselves may need replacement.