Yes, every standard electric water heater has a built-in thermostat that lets you control the water temperature. Most models actually have two thermostats, one for the upper heating element and one for the lower. These aren’t digital displays or convenient dials on the outside of the tank, though. They’re tucked behind metal access panels on the side of the unit, which is why many homeowners don’t realize the controls exist.
Where to Find the Thermostat
On a typical tank-style electric water heater, the temperature controls sit behind one or two metal access panels screwed into the side of the tank. The panels are usually about the size of a small book. Once you remove the screws and pull off the panel, you’ll likely find a layer of insulation underneath. Behind that insulation is the thermostat with a temperature dial or an adjustable knob.
If your heater has two heating elements (most residential models do), there will be two separate access panels, one higher on the tank and one lower. Each panel covers its own thermostat. You’ll need a flathead screwdriver or a Phillips head to remove the panel covers, and a flathead screwdriver to turn the temperature dial itself, which is typically a small recessed slot rather than a finger-friendly knob.
How the Two Thermostats Work Together
The upper and lower thermostats don’t operate at the same time. They follow a priority system. When the tank is full of cold water, the upper thermostat activates first and heats the top portion of the tank to its set temperature. Once that target is reached, it switches power down to the lower thermostat, which then heats the bottom portion of the tank.
During normal use, cold water enters through the bottom of the tank. The lower thermostat detects the temperature drop and kicks on the lower element. But if you’ve used a large amount of hot water and the upper portion cools down significantly, the upper thermostat takes priority again, heats the top section first, then hands off to the lower element. This design ensures you get usable hot water from the top of the tank as quickly as possible, since that’s where the outgoing hot water pipe draws from.
Both thermostats should generally be set to the same temperature. If they’re mismatched, you can get inconsistent hot water or force the system to cycle inefficiently.
What Temperature to Set
Most manufacturers ship water heaters preset to 120°F (49°C), which is the setting that balances comfort, energy savings, and safety for the average household. But the right temperature depends on your situation.
The CDC recommends setting your water heater to at least 140°F (60°C) to prevent the growth of Legionella, the bacteria that causes Legionnaires’ disease. At temperatures below 120°F, these bacteria can thrive inside the tank. The tradeoff is that water at 140°F can cause a third-degree burn in just 5 seconds. At 120°F, it takes about 10 minutes to cause the same injury. Here’s how quickly scalding can happen at different settings:
- 120°F: roughly 8 minutes to cause a second-degree burn
- 124°F: about 2 minutes
- 131°F: about 17 seconds
- 140°F: about 3 seconds
- 150°F: less than 1 second
If you have young children, elderly family members, or anyone with reduced sensation in their skin, the risk of scalding at higher temperatures is real. One solution is to set the tank to 140°F for bacterial safety and install a thermostatic mixing valve at the heater’s outlet. This valve blends hot and cold water automatically to deliver a safer temperature (typically around 120°F) to your faucets and showerheads, while keeping the stored water hot enough to prevent bacterial growth.
How to Adjust the Temperature
Before you start, turn off the power to the water heater at the circuit breaker. Electric water heaters run on 240 volts, and the wiring behind the access panel is exposed. This is not a step to skip.
Remove the access panel screws and set them aside. Pull back or remove the insulation to expose the thermostat. You’ll see a temperature dial with markings, sometimes in degrees and sometimes just with labels like “warm,” “hot,” and “very hot.” Use a flathead screwdriver to turn the dial to your desired setting. If your heater has two thermostats, repeat the process on the second panel and set it to the same temperature.
Replace the insulation and panels, restore power at the breaker, and give the tank a few hours to reach the new temperature before testing at a faucet with a kitchen thermometer. If the water is too hot or too cool, repeat the process in small increments.
Smart Water Heaters Add Digital Controls
Newer electric water heaters from brands like Rheem now come with Wi-Fi connectivity and app-based controls. Instead of opening access panels and turning a dial with a screwdriver, you can adjust the temperature from your phone, set schedules so the heater runs at lower temperatures when you’re away and ramps up before you get home, and monitor energy usage in real time. Some models also work with voice assistants like Alexa and Google Home.
These smart models often include built-in leak detection that can alert your phone within 15 seconds of detecting a problem. Higher-end versions feature automatic shut-off valves that limit water loss to about 20 ounces if a leak is detected. The temperature control on these units is the same thermostat-and-element system underneath, just with a digital interface layered on top. If you’re replacing an older unit and want easier day-to-day temperature management, a smart model eliminates the need to ever open an access panel again.