Homeowner guide · Water heaters
What temperature should your water heater be set to?
For most homes, 120°F is the water heater temperature setting public guidance lands on. It balances energy cost, scald risk and bacteria control. Here is what the sources say, when a different setting might fit your household, and how to change it.
Key takeaways
The short version
- The NJ Department of Health recommends a minimum of 120°F.
- It notes a setting above 120°F may be better for controlling bacterial growth.
- Montana’s weatherization program says turning down to 120°F cuts water-heating costs by 6 to 10 percent.
- A 140°F setting is mainly needed for a dishwasher without a booster heater, per the same program.
- Households at higher scald risk can consider a mixing valve.
The short answer: 120°F
Two public sources point to 120°F from different directions. The New Jersey Department of Health recommends setting the water heater to a minimum of 120°F (NJ Department of Health). Montana’s weatherization program, run with Montana State University Extension, advises turning the temperature down to 120°F to reduce costs (Montana Weatherization / MSU Extension).
So 120°F works as a floor for health and as a target for energy savings. Most households can start there.
When a higher setting can make sense
Bacteria control
The NJ Department of Health says setting the heater higher than 120°F may be better for controlling bacterial growth.
Dishwashers without a booster
Montana’s program says heaters are often set to 140°F, but that is only necessary when a dishwasher lacks a booster heater.
If you raise the setting, the scald risk rises too. The NJ guidance suggests a mixing valve for households with members at increased scalding risk, such as young children (NJ Department of Health).
What turning it down saves
| Change | Effect (Montana weatherization program) |
|---|---|
| Lower the setting to 120°F | Cuts water-heating costs by 6 to 10 percent |
| Insulate the tank | Reduces standby heat loss by 25 to 45 percent, saving about 4 to 9 percent |
| Insulation kit cost | About $10 to $20, often paying for itself in under a year |
The same program says water heating can account for up to 20 percent of a home’s energy use (Montana Weatherization / MSU Extension).
How to check and change the setting
- Find the temperature dial on a gas heater, or the thermostat behind the access panels on an electric heater. Follow the manufacturer’s instructions, especially for electric units.
- Before you turn it down, mark the original setting with a permanent marker so you can return to it, as Montana’s program suggests.
- Wait a few hours, then test the water at the tap farthest from the heater with a kitchen thermometer.
- Adjust in small steps until you reach the temperature you want.
If you are not comfortable opening an electric heater’s access panel, leave it to a plumber.
Sediment matters too
The NJ Department of Health says sediment buildup in a water heater can promote the growth of waterborne bacteria, which can cause illnesses such as Legionnaires’ disease. It advises that people at increased risk, such as those 50 or older, smokers, or anyone with a weakened immune system or chronic lung disease, should not take part in draining and flushing the heater (NJ Department of Health).
Our guide on flushing a water heater, publishing November 1, covers the steps.
When to call
Water too hot, not hot enough, or running out?
We service and replace gas and electric water heaters for homes in Wayne, Strafford, Paoli, Chesterbrook, Berwyn and Devon. Call (610) 788-0042.
Frequently asked questions
Water heater temperature questions
Answers by John, Tredyffrin Easttown Plumber.
What temperature should a home water heater be set to?
120°F is the common recommendation. The NJ Department of Health recommends a minimum of 120°F, and Montana’s weatherization program recommends turning down to 120°F to save energy.
Is 140°F too hot for a water heater?
It raises scald risk and energy use. Montana’s weatherization program says 140°F is only necessary if your dishwasher lacks a booster heater.
How much do I save by lowering my water heater to 120°F?
Montana’s weatherization program says it cuts water-heating costs by 6 to 10 percent.
Can a higher setting help with bacteria?
The NJ Department of Health says a setting above 120°F may be better for controlling bacterial growth. If you go higher, consider a mixing valve to reduce scald risk.
What is a mixing valve?
A valve that blends hot and cold water before it reaches the tap. The NJ Department of Health suggests considering one for households at increased scalding risk, such as those with young children.
Sources
Where these facts come from
Every figure and rule in this guide comes from the public sources below. Rules and fees can change, so confirm with the source before you act.
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Our service area
Plumbing across Tredyffrin Township, PA
Tredyffrin Easttown Plumber serves every neighborhood in Tredyffrin Township, including Wayne, Strafford, Chesterbrook, Paoli, Berwyn, Devon, Daylesford, and Howellville, plus neighboring Easttown Township. Our office is at 217 Conestoga Rd, Suite 10, Wayne, PA 19087.
