How long does a water heater take to heat up?

As you can easily imagine, water heaters don’t have a standard heating time. The time they need to heat the water can vary depending on a lot of factors.

Therefore, in this article on how long does a water heater take to heat up, we’re providing an average time, but we’re also focusing on those factors that affect the water heating time.

This way, perhaps, you could even act on those factors to obtain a quicker heating system.

For example, according to, For every 10ºF reduction in your water heater temperature, you can save approximately 3%–5% on your water heating costs.

Let us look at more such factors and information on the water heater below!


How long does a water heater take to heat up?

Let’s start with the reason why you end up in this article: how long does a water heater take to heat up?

Well, the average time is 30 minutes. However, as we’ve mentioned, optimized systems can be even quicker and take only 20 minutes to heat up.

On the contrary, if your unit is particularly big or if there are some issues, the process can be long and take even 40 minutes or more.

Now, it’s important to know what factors affect the heating time. If you can act on any of these factors to improve your water heater’s performance, you should absolutely do it: improving the performance not only means that the water heats up more quickly but that your system becomes optimized and, therefore, energy-saving.

As you may know, energy saving always determines money saving, especially in the long term. 1

Tips from Reddit users

How long should it take for hot water tank to heat up?
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Types of Water Heaters & their Heating Times

Types of Water Heaters & their Heating Times

Different types of water heaters take different times to heat up; let us have a look at the heating time of water heaters based on their time:

  • Gas Water Heaters: The gas heater takes up to 30-40 minutes to heat the tank completely.
  • Electric Water Heaters: Electric heaters ideally take twice as much time as a gas heater. So you can expect electric water to heat the tank completely in 60 minutes or 80 minutes.
  • Solar Water Heaters: Solar water heaters use sunlight to heat water, and because they are connected to electric water heaters, they take the same amount of time (60-80 minutes) to heat up the tank. However, on a cloudy day, it might take even more time.

Tankless water Heaters

Tankless water heaters are designed in such a way that they do not require any warm-up time and provide hot water on demand. So in the case of tankless water heater, you will not have to wait around for hot water. 2

Factors that affect the heating time

1. Dimensions of the tank

Of course, if you have a smaller tank, it’ll take a shorter time to heat it up. You can consider these average times:

  • 40-gallon tank: 30-40 minutes heating time;
  • 50-gallon tank: 40-50 minutes heating time;
  • 80-gallon tank: 60-70 minutes

In most houses, the water heater features a 40-gallon tank; that’s why the average heating time is considered to be between 30 and 40 minutes, as we’ve mentioned in the previous paragraph.

2. Original water temperature

All houses are connected to the town or municipal water system. Water flows and enters your house at a certain temperature. Of course, the higher this temperature, the quicker the heating time.

This also means that you can expect shorter times during summer and longer during winter because – of course – water would flow inside municipal tubes at a higher or lower temperature, respectively, during summer or winter.

3. Power source

As you may know, water heaters can heat water through electricity or gas. Gas water heaters are more efficient, and therefore they can take shorter times to heat up the water.

On the contrary, if you have an electric water heater, you can expect longer times. This is why gas water heaters are considered more efficient.

4. First-hour delivery rate

The first-hour delivery rate or FHD rating is a parameter that can tell you how powerful your water heater is. By powerful, we mean quick when it comes to heating water.

The FHD rating tells how many gallons of water the unit can heat in an hour. Of course, the higher the FHD, the shorter the time it’ll take to heat up the water.

Also Read: How Does A Hot Water Heater Work?

Reasons Your Water Heater is Heating Slowly

Reasons Your Water Heater is Heating Slowly

Let us have a look at the reasons due to why your water heater might be heating up slowly:

  • An old water heater: One of the most common reasons for a water heater not heating up is its age. On average, a water heater lasts for 12-15 years. If your water heater has crossed this timeline, then that might be the reason for its decreased efficiency. In such cases, it is better to replace your water heater.
  • Low volume restrictor: Appliances such as shower heads and faucets consist of devices that restrict the flow of water through them, and this might be causing a delay in receiving hot water. You can call your plumber to check this if that’s the case.
  • Sediment Buildup: Water consists of minerals and other things which can lead to a sediment buildup in the heater. If left unchecked, this could cause not only slow heating but also leakage. To avoid this problem, make sure to drain or flush your heater each year.
  • Distance: Water from the heater travels up through pipes and faucets, and if your shower head or faucet is situated far away from the heater, then this could be causing delayed heating.
  • Small size of heater: You might not be getting enough hot water due to the small size of your heater. If you have a large family and you have purchased a small heater, then upgrade to a larger water heater.
  • Setting: If you are sure none of the above-mentioned things are causing low heating, then there might be some problem within the heater itself, and it is best to call a plumber and get it checked in such a case. 3

How to Increase Hot Water Temperature in Water Heaters?

Tips to Speed up Water Heater

You can try the following suggestion to speed up your water heater:

  • Upgrade to a Tankless Water Heater: These water heaters are designed in a unique way to provide hot water on demand and do not require additional heat-up time. Which means you will not have to wait to get hot water.
  • Upgrade to a Larger Tank: Again, the size of the water tank matters a lot. If you have a family of 4-5 people and are using a water heater with a capacity of 20-30 gallons, then you will run out of hot water. So if this is the case, consider upgrading to a larger tank.
  • Start Flushing your Heater Tank: Many homeowners do not understand the importance of this. Water heaters start accumulating sediments that restrict their heating and cause leakage, cracks, and corrosion. So make sure to flush your water heater tank once a year at least. You can do this yourself or call a plumber.
  • Use Recirculators: You can get a hot water recirculation system installed in your bathroom. Recirculation moves hot water quickly, and it even moves unused hot water toward the faucet. 4

How to Reset an Electric Water Heater?

Wrap Up

Water heaters may seem like simple appliances, but they can cause some problems which can be solved with a little knowledge about them.

In this article on how long does a water heater take to heat up, we not only shared the heating time of different types of heaters with you but also gave you shared tips on what might be causing the issue and how you can solve it. We hope you found this useful.

Also Check Out 10 Best 70-Gallon Water Heaters 


How long does a Tankless Gas Water Heater take to warm up?

Tankless Gas Water Heater supplies hot water “on-demand,” which means you will not have to wait for thetake water to get heated up and will get hot water as and when you need it.

How long does an Electric Gas Water Heater takes to warm up?

Tankless Electric Water Heater supplies hot water “on-demand,” which means you will not have to wait for thetake water to get heated up and will get hot water as and when you need it.

Why do I get only 10 minutes of hot water?

If your hot water is not lasting long, then it could be due to the following reasons:

  • You are overusing hot water.
  • Your water tank is small.
  • Your water heater tank has a sediment build-up. 5
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