How Long Does Water Stay Hot in a Hot Water Heater?

Do you have a power blackout and want to know how long the water in the electric heater will stay hot?

Or, the temperature of the hot water without power is falling fast and you are looking for ways to make it last for longer?

Either way, it is useful to know how long the water in the electric hot water heater can last. Different heater designs have varying standby energy losses that largely determine how long the water stays hot.

In this article, you will learn how long hot water in an electric water heater without power lasts and ways to make it stay hot for longer in case it is losing heat fast!

Why Your Hot Water May Be Getting Cold Quickly

If your hot water is getting cold quickly, it may be because of the following reasons:

# 1. Low uniform energy factor of the water heater

Similarly, if an electric water heater has a low uniform energy factor and poor insulation then the stand losses are high and the water temperature will drop quickly

To keep the water hot for as long as possible, always aim to purchase a water heater with the highest uniform energy factor.

The energy efficiency of the heater is always expressed as the uniform energy factor.

This determines how much energy the heater uses to heat water and how long it stays hot once heated.

Heaters with a higher uniform factor are more efficient with lower standby energy losses and cost less to use.

A heater with a uniform energy factor* of 0.93 is more efficient than one with 0.58.

You can usually find the energy efficiency and uniform energy factor in the water heater’s electrical specifications and energy guide that part of the heater’s documentation.

# 2. Low insulation thickness of the water heater

The water heater may not have enough insulation,

Some local codes may require that insulation blankets be applied to a particular water heater model to minimize the heater’s standby loss.

This will be the case if the particular model does not meet the minimum standards for National Appliance Energy Conservation Act standards.

Check the water heater owner manual if the heater meets the standard or requires additional insulation.

Some water heaters also need sections of additional insulation to be installed along the cold and hot water pipes from the heater to improve energy efficiency.

# 2. Using a water heater with a FHR that does not match the home hot-water needs at peak demand

Always check the heater’s FHR and confirm that it can meet the hot water needs at the peak before purchase.

Some heaters can supply a larger volume of hot water in the first hour of use than others.

For these heaters, the water lasts longer before the temperature drops significantly.

When this is combined with the rate of usage of hot water, the higher the rate of usage, the shorter the duration that hot water lasts in the heater.

Therefore heaters with a high First Hour Rating (FHR) are better suited to meet the hot water demands of a larger family at peak demand than those with a lower FHR.

# 3. The ambient temperature is lower than usual

If the heater is installed in an environment with lower ambient temperatures then the temperature of the hot water will last a shorter time than when in a colder environment.

If you live in the colder northern parts of the USA, you may have to install insulation blankets to keep the water hotter for longer – check your local codes and your heater’s owner manual for guidance.

The hotter the surrounding temperature, the longer the water in the heater can stay hot.

You can therefore expect the water in the heater to stay hotter in the summer than in the winter.

*Uniform energy factor is a rating system used by the Department of Energy (DoE) to specific the energy efficiency of a water heater system and indicates the associated costs of operating. A high uniform factor indicates a more efficient unit that costs less money to operate than a low factor.

Related Questions

1. How Long Water in a 40-Gallon Water Heater Stays Hot (without Power)?

Whereas hot water heaters are insulated, some better than others, it is difficult to say how long water in the 40-gallon water heater will stay hot for.

This duration depends on the several factors at play in your unique situation such as how well insulated the heater is, the ambient temperature where you live and the heater is installed, and the usage of the hot water.

2. How Long Water in a 50-Gallon Water Heater Stays Hot (without Power)?

There is no one answer to how long water in the 50-gallon heater stays hot.

It depends on how well insulated the heater is, the ambient temperature where you live and the heater is installed, and the usage of the hot water.

3. How Long Water in a 30-Gallon Water Heater Stays Hot (without Power)?

This really depends, it can be several minutes to hours depending on how well insulated the heater is, the ambient temperature where you live and the heater is installed and the usage of the hot water.

Related questions:

What to Do if Hot Water Tank Not Keeping Water Hot

If the heater water is not staying hot, this might be because of several factors ranging from:

  • The reduced heating efficiency of the heater element. If the heater element is coated with mineral buildup depending on the quality of the water where you live then the water from the heater will not be as hot as usual.
  • Check that the water heater thermostat settings are set as expected. If the thermostat(s) are set to a lower temperature, then the water temperature will not be as hot as expected.
  • Additional insulation may be required for the heater. Check the water heater owner manual and local building and plumbing codes where you live if additional insulation is recommended for your electric water heater.

Final word

How long the water from your electric heater stays hot depends on several factors including its efficiency rating or uniform energy factor, the ambient temperature, and the usage of hot water.

So, it is not possible to specify how hot it can stay as this depends on the water heater design (uniform energy factor), ambient temperature, and usage of hot water.

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