Does Cold Weather Affect Your Water Heater? What You Need to Know

Cold mornings, lukewarm showers and a higher energy bill: winter is when most people start wondering about their water heater. Here is what the cold really does to it, what to change and what to leave alone.

Editorial Research

Written by

Lena Thornton, Weather Station Analyst & CWOP Contributor

Based on

U.S. Department of Energy water heater guidance, CPSC tap water scald advice, FEMA emergency water advice, Navien and Rinnai freeze protection information, and American Red Cross cold weather tips

Research last verified

October 24, 2026

Why Winter Makes Your Water Heater Work Harder

A water heater has one job: take cold water and make it hot. In winter the "cold" part gets colder, because the water in the mains and the pipes cools down with the weather.

So every gallon needs a bigger temperature jump to reach your setting. A tank heater needs more time to recover after a shower, and you may notice the hot water running out sooner when two people shower back to back.

There is a second effect. A tank keeps hot water waiting all day, and it slowly loses heat through its walls. Energy experts call this standby loss. A tank in a cold garage or basement loses more heat than one in a warm utility room, so it fires up more often just to stay hot.

None of this means your heater is failing. It is a bit like your car in January: it still works, it just uses more fuel to get going.

Should You Turn It Up in Winter?

Usually not. The U.S. Department of Energy's guidance for home water heaters is simple: for most residential use, set the temperature at 120°F.

120°F is also the safety number. The U.S. Consumer Product Safety Commission (CPSC) urges people to set water heaters to 120°F to cut the risk of tap water scalds. Hotter water burns skin much faster, which matters most for young kids and older adults.

There is one honest trade-off. The same Department of Energy guidance notes that Legionella bacteria (the cause of Legionnaires' disease) can grow in water heaters, and higher temperatures limit that growth. But hotter water raises the scald risk, especially for young children and the elderly. That is why some installers store water hotter and add a mixing valve set to 120°F at the outlet. If someone in your home has a health concern, ask a plumber which setup fits.

If you simply run out of hot water on cold mornings, try spacing showers a little before you turn the dial up. Turning it up costs energy every hour of the day, not just during the morning rush.

Tip: the numbers on a tank dial are often vague. Check the real temperature with a kitchen thermometer under the hot tap, then adjust.

Insulate the Tank and the Pipes

If your heater sits in a cold space, insulation is one of the cheapest winter upgrades. Start with the pipes, then look at the tank.

• Touch test: if the tank of an older electric water heater feels warm on the outside, heat is escaping, and an insulation jacket can help. Follow the instructions of the jacket and of your heater.
• Heat pump water heaters: do not wrap them. The Department of Energy warns that a blanket restricts airflow, lowers efficiency and could void the warranty.
• Gas heaters: never cover the top, the burner area or the controls of a gas heater. When in doubt, follow the manual or ask a plumber.
• Pipes: insulate the water pipes connected to the heater, especially where they run through a garage, crawl space or outside wall. Both Navien and Rinnai point out that the pipes outside the unit are the part most likely to freeze.

Tankless Water Heaters and Freezing Weather

Tankless heaters handle cold incoming water fine, but they have one winter weak spot: their built-in freeze protection needs electricity.

Navien says plainly that if you lose power during a freeze, the internal protection fails, and the unit should be drained right away (or protected with a battery backup). Rinnai also asks for a continuous power supply and describes a drain procedure for outages: shut off the water and gas, turn off the controller and the power, close the isolation valves, then open the pressure relief and drain valves. The exact steps differ per model, so keep your manual where you can find it in the dark.

• Leave the power on, even when you are not using hot water.
• Units in garages or outdoors are at the highest risk, according to Navien.
• The freeze protection does not cover the pipes leading to the unit. Insulate them.
• Rinnai also advises keeping the vent termination and condensate drain clear of snow and ice.

Snow, Vents and Carbon Monoxide

Many gas water heaters, tank or tankless, vent through a side wall instead of the roof. After a snowstorm, that little pipe on the outside wall can end up under a drift.

A blocked vent can make the heater shut down, and in the worst case exhaust gases can build up indoors. Clear the vent gently with a broom or your hands after heavy snow, and do not pile shoveled snow against that wall.

A working carbon monoxide alarm near sleeping areas is your backup. Carbon monoxide has no smell or color, so you will not notice it on your own.

When the forecast shows a winter storm, it is worth knowing what the alerts mean. Our explainer on watch vs warning vs advisory tells you how much time you have to get ready.

Leaving Home in a Cold Snap

Frozen pipes are the most expensive winter surprise, and they often happen when nobody is home. The American Red Cross advises keeping the heat on, set no lower than 55°F, when you leave home during cold weather.

A quick myth check: a strong wind does not push pipes below the real air temperature, it only makes them cool down faster. Our page on wind chill explained shows why.

• Do not turn the water heater off "to save energy" if it sits in a space that can freeze. A tank that goes cold in an unheated garage can freeze along with its pipes.
• Many newer water heaters have a vacation mode that lets the water cool down while you are away and keeps the unit running. Check your manual for it.
• Open cabinet doors under sinks on outside walls so warm air reaches the pipes.

A freeze warning in your forecast is the signal to check all of this before you go.

Power Outage? Your Tank Is a Water Reserve

Here is a winter bonus most people forget: a tank water heater holds tens of gallons of clean water. FEMA confirms that you can safely drink water from your home's water heater tank when you run short of clean water.

• This only works if the water supply was not contaminated. If your water company issues a boil-water notice, treat the water before drinking it.
• Before you drain water from the tank, turn off the electricity (at the breaker) or the gas to the heater. Heating an empty tank can damage it.
• Water from the drain valve at the bottom can carry some sediment. Let it settle or pour it through a clean cloth.
• Do not drink water from radiators or a boiler heating system. FEMA warns that this water is not safe.

Refill the tank and make sure it is full before you switch the power or gas back on. Your manual describes the exact steps for your model.

Quick Winter Checklist

1. Check the real hot water temperature at the tap. Aim for about 120°F unless you have a reason for more.
2. Insulate pipes in unheated spaces, and consider a jacket for an older electric tank that feels warm (never on a heat pump model).
3. Tankless owner? Keep the power on and know how to drain the unit.
4. After snow, clear any wall vent and check that your carbon monoxide alarm works.
5. Going away in a cold snap? Keep the heat at 55°F or higher.
6. Remember the tank as an emergency water source during an outage.

Sources

• U.S. Department of Energy (FEMP): Purchasing Energy-Efficient Residential Water Heaters
• U.S. Consumer Product Safety Commission: Tap Water Scalds
• FEMA: What are emergency water sources if I'm running out of clean water?
• Navien: Tankless water heater frozen
• Rinnai: Protect Your Rinnai Product During Extreme Cold Temperatures

More cold weather basics: Frost advisory vs freeze warning · Watch vs warning vs advisory