How Long Does it Take for a Water Heater to Heat Up?(2024)

Updated on:
January 6, 2024

In a modern world full of creature comforts that work at our convenience, waiting for your water heater to heat up is quite irritating. There’s hardly anything more infuriating than getting ready for a hot bath or shower only to realize that the water is still cold!

Every time you turn on a faucet or shower, you’re probably wondering how long it should take your water heater to heat up, especially after it runs out of hot water.

The answer is both easy and complicated: easy because I can offer a numerical estimate, complicated because it depends on the type of water heater.

Let’s examine this subject in further detail, beginning with the factors that determine how long your water heater takes to heat up.

Reasons Your Water Takes Longer to Heat Up

I should mention that the anticipated wait time is only a rough estimate. Several factors may affect the time required for a water heater to heat up, also called the hot water heater recovery time. Some are universal, while others are more specific.

These factors include the following:

1. The size of the water heater

Tank size is an important factor that may impact the heating time of a water heater. A larger storage tank requires more time to heat up. This is due to the higher quantity of water available to heat. Larger tanks generally contain two heat sources or a massive burner to facilitate a speedier recovery process.

In contrast, a smaller tank will heat up quicker but likely run out of hot water faster than the larger tanks. So, although you may get hot water in a shorter amount of time, you will likely run out after completing a few basic tasks.

Finally, there are tankless water heaters. These hot water heaters basically heat water using gas or electrically heated pipe systems, eliminating the need for a tank. This implies that water is continually heated as it moves through the system rather than being slowly heated in a tank. This drastically decreases the time it takes to get hot water (as little as 15 seconds!), but it also reduces the water flow rate.

2. The first-hour rating

The first-hour rating implies how many gallons of water the water heater can provide in the first hour of operation. It indicates the capability of the water heater to restore a full tank to the desired hot water temperature. A high rating during the first hour implies a shorter wait for hot water. The tank capacity, fuel supply, and size of the gas burners all influence this figure.

3. Incoming water temperature

Both tank and tankless water heaters’ heating times are affected by the initial temperature at which the water is heated. 

Keeping in mind that tank water heaters are designed to hold water and heat it regardless of the outside temperature, it’s safe to assume that they will perform adequately in any climate. Tankless heaters, on the other hand, only increase the flow rate when hot water is needed. This implies that if the groundwater temperature is low, the water may not heat up as expected. 

Both water heaters are susceptible to damage from very low temperatures in the regions or sections of a building where they have been stored.

4. Pipe diameter

The length of time it takes for a water heater to heat up might be affected by the diameter of your water pipes rather than the height of your piping. A larger pipe diameter is great because it delivers more water. However, more energy will be required not only to heat the water but also to force it through the larger pipes and the rest of the plumbing.

How Long Does a Water Heater Take to Heat Up?

Now, let’s return to the original question: how long should it take your hot water heater to heat up? I’ll answer this question by examining each type of water heater and how long they take to do their thing.

Gas tank water heater

A liquid propane or natural gas burner positioned underneath the sealed tank heats the dense, cold water at the bottom of the gas tank heater. 

As the water heats up, it rises to the top of the tank, where the hot water discharge pipe draws it off to supply hot water wherever it is needed. The hot water discharge pipe is much shorter than the dip tube because its purpose is to funnel off the hottest water located at the top of the tank.

Once water enters the tank, the typical gas heater takes 30 to 40 minutes to heat the water. This initial heating occurs when fresh water from the water supply is added to the tank.

For a more precise explanation of why this takes 30 minutes, I have to get a bit technical. 

As we’ve established, the size of the water heater’s tank is a significant factor, as more water takes longer to heat. The second important consideration is the BTU (or British Thermal Unit) rating of the heater. A BTU is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. A water heater with higher BTUs may heat water more quickly. For example, the most popular tank size for a gas tank heater is 40 gallons. There are about 8.3 pounds of water per gallon, so a 40-gallon tank must heat around 330 pounds of water.

Simply put, a 40,000 BTU burner system in a 40-gallon tank needs 30 seconds to heat each gallon, resulting in a heating period of half an hour.

If you have a smaller tank or a high BTU rating, the warm-up time for your hot water heater will be substantially shorter. However, if you have a larger tank or a lower BTU rating, it will take longer to heat your tank.

Electric tank water heater

An electric water heater functions similarly to a gas water heater. It delivers unheated water into the tank via the dip tube and warms it using electric heating elements inside the tank. Through the heat-out pipe, the hot water rises in the tank and is distributed throughout the house.

Typically, tank-style electric water heaters need twice as much heating time as gas water heaters. Although electric heating elements are often more cost effective, they cannot compete with the superior performance of gas-fired systems. It takes an average of 60 minutes to heat up a 40-gallon electric water heater.

This is why homes with significant water needs often opt for a gas tank water heater rather than an electric one. Electric water heaters are ideal for smaller dwellings with lower water demands.

Gas tankless water heater 

Gas tankless water heaters work the same way as conventional gas water heaters, the only difference being the lack of a storage tank. They save energy by only heating water when it is needed. This means that no energy is wasted when the water heater is on standby. When a hot water tap is turned on, cold water is drawn into the water heater. The gas burner is turned on automatically by a flow sensor, which then warms up the heat exchanger. The incoming cold water encircles the heat exchanger and leaves the water heater at the desired hot water temperature.

Since tankless hot water heaters heat water on-demand, the only thing that determines how long it will take for hot water to flow from your faucet is the distance between your water heater and the fixture being used.

If the tankless gas water heater system is functioning properly, this should not exceed a few seconds for a standard house (around 15 seconds). With a large home, it may take a few more seconds for hot water to flow through the pipes and reach items further from the heater.

A tankless gas water heater heats water instantly, so it should only take a few seconds for the hot or warm water to travel through the pipes and into the faucet.

Electric tankless water heater

As incoming cold water flows into the electric tankless water heater, it passes by an inlet thermostat, which measures the temperature of the cold water. The water then flows from the intake pipes into the heating chambers. Electric heating elements warm up the copper coils in the heating chamber, which in turn heats the water.

Depending on the size of your tankless electric water heater, there are roughly four heating chambers. The hot water leaves the chambers and goes through the discharge line. Here, another thermostat checks the water temperature to make sure it is at the right level.

A tankless electric hot water heater works the same way as a tankless gas heater. It heats water on demand. To put it simply, the water won’t get warm until you turn on the dishwasher or the hot water faucet.

Most of the time, an electric tankless heating system will heat water in a few minutes. However, since gas is a superior heat source, it can take a little longer for a tankless electric heater to heat the water. You should also factor in the distance the hot water takes to travel through the piping as that too can affect the hot water wait times.

Solar water heater

Although gas and electric water heaters are the most common, there is a variety of other water heating equipment in use in the United States today.

Concerns about energy efficiency and climate change have led to a growth in the use of solar water heaters. Solar panels harvest sunlight and use it to heat water (normally on the roof of the building). As a result, the water in the storage tank may be heated using just the sun’s rays.

Typically, a solar water heater will work in tandem with a conventional electric hot water heater. The main reason for this is the inefficiency of collecting solar energy at night and, especially, during the winter. Reheating water might be necessary if the temperature is insufficient. As a consequence, a secondary heating system is essential. Due to this, the typical solar water heater has the same 60–80 minute heating time as an electric water heater.

Final Thoughts

So, how long does it take for a water heater to heat up? A typical 40-gallon gas water heater can heat water in 30 minutes, but a comparable electric water heater may take up to an hour. Tankless water heaters are significantly faster, heating water in around 15 seconds on average, but at the expense of slower water flow. Meanwhile, solar water heaters are similar in heating time to electric models due to the use of electric water heaters as backups. 

There is a heater on the market that will meet the needs of every American household. Before settling on a traditional tank or a tankless water heater, it’s important to evaluate your hot water demands.

Now that you understand how long it takes for a water heater to heat up, check out my reviews of the best tankless water heaters and the best 50-gallon water heaters to find out the best models on the market.

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