How Long Does It Take a Water Heater to Heat?

Are you worried that your water heater is taking too long to heat up? Do you feel like replacing it with a new one? Well, before taking that path, how about finding out why it’s taking that much time to heat up? You might be surprised to find out that it isn’t much of a problem after all.

How Long Does It Take a Water Heater to Heat

Water heaters come in a variety of types, sizes and use varying fuel/power sources. They play a very important role in our everyday life and hence a worthy investment.

But then, we’ve all encountered this worrying situation. Everyone wants to get ready in the morning, but there’s no more hot water. The water heater seems to be taking too long to heat the water. What could be the reason?

In this post, we discuss the factors that influence how long a water heater takes to heat water.

Factors That Influence the Time a Water Takes to Heat Up

Water heaters are affected by varying factors that can influence their heating time. Some of these factors are universal across different types (of heaters), while others are specific.

They include:

Size of the Water Heater

The larger the water heater, the longer the time it’ll take to heat up. This is because; the bigger it is, the more water it needs to heat.

Smaller tanks heat up pretty fast. The only downside of these smaller models is that they run out faster. Therefore, although you’ll have hot water within minutes, you’ll run out after carrying out minor tasks.

First Hour Rating

The first hour rating will tell you the gallons your heater can deliver within the 1st hour. The higher the first hour rating, the shorter the time it takes to heat water.

Inlet Water Temperature

The inlet temperature rise /temperature rise can influence the time it takes for your water heater to heat up. With temperature rise, we refer to the difference between the temperature of the incoming water and the preset temperature of the heater (the temperature you want the water to be heated).

The higher the temperature rise, the longer the time your heater will take to heat up.

Fuel Type

Fuel type greatly influences the recovery time of your water heater. Gas heaters heat water faster than their electronic counterparts do. This is because the gas burners present in a gas water heater can reach a higher temperature than the electric resistant coils present in an electric water heater.

What Should You Do If Your Water Heater Suddenly Takes Longer to Reheat

After using your water heater for some time, it will most likely start taking longer to heat. However, if this happens prematurely (a few weeks after purchase), you need to be concerned.

So, what do you need to do?

Check for Sediment Buildup

If your water heater suddenly starts taking longer to heat up, it’s most likely because of sediment buildup. This usually happens because of poor maintenance practices or if you have hard inlet water.

Sediment buildup occurs when calcium and magnesium (dissolved minerals) present in the water settle on the interior surfaces of your water heater. Over time, the buildup creates a thick layer of sediment that restricts the ability of our water heater to heat water.

And how do you tell that your water heater has sediment buildup?

  1. You’ll run out of hot water faster than before
  2. Your water heater will start making a popping/hissing sound
  3. You’ll start getting higher than normal energy bills

To fix this problem, ensure that you flush your water heater regularly. It’ll help to get rid of the buildup. You can also get a professional to inspect the water heater if flushing the heater doesn’t help.

In case of a broken dip tube, thermostat or bad burners, a professional will help you repair them.

The Water Heater Might Require Troubleshooting

If your water heater doesn’t have sediment buildup, it might be that the thermostat or heating element requires troubleshooting.

If using an electric heater, troubleshooting it is as simple as taking a walk in the park. All you need to do is:

  1. Turn off the power before you start handling it
  2. Get a screwdriver and remove the access panel. Then, pull out the insulation to access the upper thermostat.
  3. Get a multimeter and use it to check the wires for any sign of power. Ensure that the reading is zero before you continue.
  4. Adjust the temperature using a flat-blade screwdriver. Decrease the temperature by a few degrees.
  5. Replace the insulation as well as the access panel. After everything gets back in place, turn on the breaker and restore your water heater.

If using a gas water heater, troubleshooting it isn’t an easy task. You’ll have to seek professional help

The Water Heater Might be Too Small for Your Needs

If your water heater is too small, it might be the reason why you’re facing the problem. You might be wondering how to tell whether you have the heater is small or not. Well, get a professional to inspect it.

If small, they will suggest a better alternative (the best size) for your family. They can even provide a quote for the water heater replacement.

Incorrectly Installed Water Heater

Another reason why your water heater might be taking too long to heat up is if it was improperly installed. For instance, if the technician installed an electric water heater for you and turned on the circuit breakers before the tank was full of water, the heating element might have overheated. This limits the ability of the unit to heat quickly.

Get a professional to fix this problem as well.


All the factors discussed above determine how long a water heater takes to heat up. Although some of these factors are universal, and there’s nothing much you can do about it, you need to up your game as far as proper care and maintenance of your water heater is concerned. By doing so, you can avoid some of these problems.

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