Most water heaters ship from the factory set to 140°F, but the Department of Energy recommends 120°F for most households. Lowering the temperature saves energy, reduces scalding risk, and takes less than ten minutes on most units. The process differs slightly between gas and electric models, but neither requires special tools or plumbing experience.
Choosing the Right Temperature
The sweet spot for most homes is 120°F. At that setting, water is hot enough for comfortable showers, effective handwashing, and most household cleaning. The Department of Energy estimates that a heater set to 140°F wastes $36 to $61 per year in standby heat losses alone, energy spent keeping water hotter than you need it.
The tradeoff is bacteria. The CDC recommends storing hot water at or above 140°F to prevent Legionella, the bacterium that causes Legionnaires’ disease. Legionella can grow at temperatures as low as 68°F, and 120°F doesn’t kill it as reliably. For the general population, 120°F is considered safe. If anyone in your household has a suppressed immune system or chronic respiratory disease, 140°F is the safer choice, paired with anti-scald devices at faucets and showerheads to prevent burns.
One more consideration: dishwashers. If yours doesn’t have a built-in booster heater (check the manual or look for a “sanitize” cycle), it may need incoming water between 130°F and 140°F for proper cleaning. Most modern dishwashers have a booster, but older models might not.
How Scalding Risk Changes With Temperature
The relationship between water temperature and burn severity isn’t gradual. It’s steep. According to the Consumer Product Safety Commission, water at 150°F causes third-degree burns in just two seconds. At 140°F, it takes six seconds. At 130°F, thirty seconds. Even at 120°F, a five-minute exposure can cause third-degree burns, though that’s far less likely during normal use since most people pull away from uncomfortable water well before that point. Every 10-degree reduction buys significantly more reaction time, which matters most for young children and older adults who may not move away from the tap quickly.
Lowering Temperature on a Gas Water Heater
Gas water heaters have a temperature dial on the front of the gas control valve, near the bottom of the tank. On some models, the dial shows actual degree markings. On others, you’ll see labels like “Low,” “Medium,” “Hot,” and “Very Hot” without specific numbers. If your dial uses labels, check the owner’s manual for what each setting translates to in degrees. As a general reference, the midpoint or “warm” setting on many tanks corresponds roughly to 120°F, but this varies by manufacturer.
To adjust, simply turn the dial to your desired setting. No tools are needed. Mark the current position first (a small piece of tape or a marker line works well) so you can return to it if the new setting doesn’t feel right. After adjusting, wait at least two hours before testing. The tank needs time to settle to the new temperature.
If the Dial Is Stuck
Temperature knobs on gas heaters can seize up from mineral deposits, especially on older units. If yours won’t budge, pull the plastic knob off the stem and spray the joint where the stem enters the valve with a penetrating oil like PB Blaster (not WD-40, which doesn’t penetrate corrosion as well). Spray it several times over the course of two to three days, gently trying to rotate the stem between applications. Once it loosens, replace the knob and adjust normally. If the valve still won’t move, the internal mixing cartridge may need replacement, which is a job for a plumber.
Lowering Temperature on an Electric Water Heater
Electric water heaters don’t have an external dial. The thermostat is behind one or two metal access panels on the side of the tank, secured with screws. Most electric heaters have two thermostats: an upper and a lower. You’ll need a flathead screwdriver or a Phillips screwdriver depending on your model.
Before opening anything, turn off the circuit breaker that powers the water heater. This is not optional. The thermostats sit next to exposed electrical wiring carrying 240 volts. Once the power is off, remove the access panel screws and set them aside. Pull back or remove the insulation behind the panel to reveal the thermostat. You’ll see a small dial or a slotted adjustment screw with temperature markings. Use a flathead screwdriver to turn it down to 120°F or your desired setting.
If your unit has two panels, adjust both thermostats to the same temperature. Setting them differently can cause inconsistent heating or force one element to work harder than the other. Replace the insulation, screw the panels back on, and flip the breaker back on. Wait two to three hours before testing.
How to Verify the Actual Temperature
The numbers on a water heater dial are approximate. The only way to know your actual output temperature is to measure it at the tap. Go to the faucet closest to the water heater and run the hot water for two to three minutes until it reaches its hottest point. Then fill a glass and check with a kitchen thermometer, an instant-read meat thermometer, or an infrared thermometer. A standard meat thermometer works fine but may take a couple of minutes to stabilize.
If the reading is higher or lower than your target, go back to the heater and nudge the dial slightly. Wait another two hours and test again. It often takes two or three rounds of small adjustments to land on the exact temperature you want. This is especially true for gas heaters with vague label markings instead of degree numbers.
What to Expect After the Change
Dropping from 140°F to 120°F is noticeable. Showers will still feel hot, but you’ll use less cold water to balance the mix, which means the hot water in your tank lasts longer per shower or dishwasher cycle. Some people find the change feels lukewarm at first simply because they’re used to hotter water, but 120°F is well above body temperature and plenty warm for daily use.
If you have a large household and find you’re running out of hot water more quickly after the adjustment, the issue usually isn’t the lower temperature. It’s that the recovery time between heavy uses (back-to-back showers, running the dishwasher and laundry simultaneously) hasn’t changed. In that case, spacing out hot water use by 20 to 30 minutes between major draws helps. Alternatively, you can split the difference and set the heater to 125°F, which still reduces scalding risk and energy costs compared to 140°F while giving a small buffer for high-demand households.