After 20-plus years on water heaters across Washington, Oregon, and California, here is a question we get all the time: what temperature should a water heater actually be set at? The short version is 120°F. It is hot enough for showers, laundry, and dishes, easy on your energy bill, and far less likely to scald someone. Below is the why, the exceptions, and exactly how to change the setting yourself.
What Temperature Should a Water Heater Be Set At?
Most new units leave the factory set around 140°F, but the U.S. Department of Energy notes that the majority of households only need 120°F. At 140°F you are paying to keep water hotter than you use it, and you are running a real burn risk at the tap. Dialing it back to 120°F is one of the cheapest efficiency upgrades there is — it costs nothing and takes about an hour.
| Setting | Best for | Trade-offs |
|---|---|---|
| 120°F | Most homes; families with kids or older adults; saving energy | Slows mineral buildup and corrosion; very low scald risk; slight (and for most people, safe) Legionella risk |
| 140°F | Dishwashers without a booster heater; immune-compromised or chronic respiratory conditions | Serious scald hazard; wastes roughly $36–$61 a year in standby heat loss; faster tank wear |
Why We Recommend 120°F
On nearly every service call, 120°F is the number we land on, and it comes down to your bill, your tank, and your safety. A heater stuck at 140°F can waste roughly $36 to $61 a year just on standby losses — heat bleeding out of the tank while you are not using it — plus more on the water you actually run. The DOE puts the total savings from turning the temperature down at 4% to 22% a year.
A cooler tank also lasts longer. Lower water temperatures slow the mineral buildup and corrosion that eat away at the tank and elements, which is a big deal in the hard-water pockets we see throughout the West Coast. And then there is the part that matters most — safety. Water at 140°F can cause a serious burn in a matter of seconds, a real concern in any home with young kids or older adults.
You can read the federal guidance straight from the source on the Department of Energy’s water-heating page.
When You Might Want It Higher Than 120°F
There are two legitimate reasons to run hotter. If you have an older dishwasher without its own booster heater, it may need water in the 130°F to 140°F range to clean properly — though most dishwashers built in the last decade heat their own water. And if someone in the household has a suppressed immune system or a chronic respiratory condition, the DOE suggests keeping the tank at 140°F to limit bacteria such as Legionella.
If you do go to 140°F, do not skip the safety step: install thermostatic mixing valves on the taps used for bathing and washing. They blend in cold water so the tank stays hot enough to hold bacteria in check while the water reaching your hands and shower stays at a non-scalding temperature. We walk through how these work in our guide to using a mixing valve.
How to Adjust Your Water Heater Temperature
The thermostat dial is rarely accurate, so do not trust the numbers printed on it. Instead, measure the real water temperature with a thermometer at the tap farthest from the heater, adjust, wait a couple of hours, and measure again. It usually takes a couple of rounds to land where you want.
Gas tank heaters: Look for the dial on the gas control valve near the bottom of the tank and turn it to your target. Electric tank heaters: Shut off the breaker first — this is not optional. Then remove the access panel(s) and peel back the insulation. Many electric units have two thermostats, an upper and a lower, and both need to be set to the same temperature. Adjust with a flathead screwdriver, then button it back up and restore power. If yours has no hot water at all once you are in there, our electric water heater troubleshooting guide can help. Tankless units: easiest of all — just set the temperature on the digital control panel.
A regional note: in Washington and Oregon, where heaters often sit in cold garages or crawlspaces, insulating the tank and the first few feet of hot-water pipe helps the water hold its heat between uses — so you keep the energy savings without lukewarm showers on a January morning. In milder Northern and Southern California, standby losses are smaller, but the 120°F setting still pays off on your bill and keeps scald risk low for the whole household.
Need a Hand? Our Certified Techs Can Help
Setting your heater to 120°F is a smart, no-cost move for most homes — hotter only when you have a specific reason and the right safety valves in place. If the dial will not hold a setting or the water never warms up, it may be a sign the unit is on its way out; our list of 10 signs it is time for water heater replacement can help you tell. Either way, the team at Fast Water Heater can handle everything from hot water tank repairs to a reliable water heater installation, with local technicians serving Washington, Oregon, Northern California, and Southern California. Find your region and contact us today to schedule an appointment.
Frequently Asked Questions
What temperature should a water heater be set at?
For most homes, 120°F. It is hot enough for showers, laundry, and dishes while keeping energy use and scald risk low. The Department of Energy notes most households only need 120°F, even though many units ship set to 140°F.
Is 120 or 140 degrees better?
120°F is the better choice for most households. 140°F only makes sense if you have a dishwasher without a booster heater, or if someone in the home has a suppressed immune system or chronic respiratory condition — and even then, pair it with mixing valves to prevent scalding.
Can a water heater be too hot?
Yes. At 140°F, tap water can cause a serious burn in just a few seconds, and the higher temperature speeds up mineral buildup and corrosion inside the tank. That is why 120°F is the recommended setting for most homes.
Does lowering the temperature save money?
It does. Turning the temperature down can save 4% to 22% a year on water-heating costs. A heater left at 140°F can waste roughly $36 to $61 annually in standby heat loss alone, plus more on the hot water you actually use.
