How Long Will Hot Water Heater Stay Hot Without Power? (Explained)

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It’s estimated that hot water can stay hot for at least a day or two without power. However, that depends on how large the tank is, the quality of your water heater tank, and the form of insulation you have. It can also depend on how much hot water you are using hot water during the power outage.

A home high efficiency furnace with a residential gas water heater & humidifier.

How Long Will The Hot Water Heater Stay Hot?

It might be difficult to provide a particular temperature loss, making it hard to estimate how long the water will remain hot.

But many water heater manufacturers show that water will lose between 1 kWh and 2.5 kWh of heat per day.

Even so, various aspects determine how long your water heater will keep water hot. For instance, cold water will start filling the water tank once you start using the heated water and lower the temperatures.

The original temperature setting before the power outage also matters- if the temperature was set high, the hot water might remain hot for a longer period.

The current temperature outside can affect how long hot water will remain hot. Very cold weather can lower the time your water remains hot during the outage. It can also affect its efficiency and over system functionality.

Moreover, the placement of your heater affects how long the water will stay hot. For example, a water heater situated in between two inner walls will keep water hot for longer than one placed at the garage.

It should be noted that in the past, regulations did not need hot water tanks to have any insulation; however, legal codes today require that insulation be incorporated with the tank when you purchase one.

So, if your water heater is a recent model, it will take longer for the water to get cold.

Does Hot Water Stop Working When Power Goes Out?

Households depend on reliable water supply outlets and appliances. But whether the hot water stops working when the power goes out depends on the type of water heater you are using and the fuel source used for the appliance.

For instance, if you’re using the conventional tank-style water heater powered exclusively by electricity, the heater will stop working in case of a power outage.

But the water that had been heated before the power went out will stay hot for some time in the tank.

Do Gas Conventional Tank Water Heaters Need Electricity?

Gas water heaters typically don’t require electricity for everyday operation as they rely on the pilot light and gas ignition for heat. Thus, they will often work during a power outage. However, most of the gas heaters use electricity to relight the pilot light.

That means the heater may not run during a power outage if the pilot light goes out.

If you notice a power cord plugged in the wall and connected to the gas water heater, it’s likely the heater relies on electricity. In such cases, it’s advised to turn off the gas supply during the outage.

Also, remember that the heater will supply hot water only for a few days after a power outage like an electric tank).

Does a Gas Tankless Water Heater Work Without Electricity?

Gas tankless water heaters use gas to heat the water and don’t rely on electricity as a fuel source to heat the water. However, these heaters have a control panel (brains of the heater) that is powered by electricity.

So, the heater won’t work independently during a power outage.

Since the heaters are tankless, there’s no reserve of heated water to pull from. Fortunately, you can run the gas-powered tankless water heater using a portable generator that powers heaters.

Alternatively, you can install a battery backup system to offer temporary power to the heater.

electric water heater

Does An Electric Tankless Water Heater Work Without Electricity?

Since the heater depends solely on electricity, it stops working immediately after the power goes off.

And since there’s no tank to pull reserve from, you’ll be stuck without hot water for the time the power is out.

Will Other Fuel-Powered Heaters Keep My Water Hot Without Electricity?

Besides gas- and electric-based, other more specific types of water heaters are available. That includes solar, heat coil, fuel oil and indirect and can keep your water hot without electricity.

But if the heaters are tankless, they use at least some electricity to power the ignition and computer controls.

And if they operate using electricity, then they’ll stop working in case power goes out. You’ll know if the heater requires electricity if you notice a power cord plugged in the wall and connected to the heater.

How Do You Know If the Water Heater Is Losing Too Much Heat During Power Outage?

If your tank is in a cupboard or closet, you can determine how much heat the tank is losing depending on how warm the area is.

An airing closet, for example, should be somewhat warm, but if it’s above 30°C, the tanks may be losing too much heat.

How Can You Keep Hot Water Hot for Long in Your Heater in Case of a Power Outage?

When the power is out, it can be crucial to turn off the power and water supply to the tank to keep the water as hot as possible. This can increase the amount of time the hot water reserve can last.

Besides, you can look for ways where you can try using less hot water. For instance, you can save the hot water for showers only and avoid running the dishwasher or doing laundry using hot water during the power outage.

You could also get everybody in your household to take shorter showers or install showerheads with low-flow rates.

A well-insulated heater tank can keep your water warm for a considerably longer period of time. As a result, you should use a high-quality tank composed of effective insulators.

Better-insulated tanks are more efficient since they lose less heat and hence need less energy to keep the water at the desired temperature without reheating it.

Alternatively, if you keep having a power outage, you can invest in an insulating jacket for the tank or add an extra blanket to the heater. If you already have the insulating jacket, try insulating the pipes by wrapping blankets around them.

How Long Will It Take for Water to Heat After the Power Is Back?

If you’re using tankless water heaters, the water will be hot again almost instantly after the power supply is connected. However, if you’re using tank water heaters, you should give the heater some time to heat more water.

Tank water heaters aren’t instant heating devices. A water heater can take about half an hour to an hour and a half to heat the tank full of water.

This varies depending on the tank size- the larger the heater, the longer it’ll take to heat up. Moreover, if the heater has a lower first-hour rating, it will take longer to heat all its water.

Furthermore, electric heaters take about twice as long to heat water as their gas water counterparts.

That’s because gas burners in gas heaters can reach a higher temperature than electric resistance coils in electric heaters quickly.