How Long Does It Take to Heat a Hot Tub?

By Calvin | Last Updated: July 18, 2021 | Guides / Hot Tub 101

Hot tubs are used with a water temperature of about 104 degrees Fahrenheit (40 degrees Celsius). But how long does it take to heat a hot tub to this level? Here is the answer to that.

It takes between 3 hours and 8 hours for a hot tub to get heated to 100 degrees Fahrenheit (or 38 degrees Celsius). On average, most hot tubs take 4 hours to get the water to 100 degrees Fahrenheit.

The time it takes for the hot tub to get to the desired temperature depends on several factors such as the size of the hot tub and the capacity of the heater.

But there is more. This post reveals all you need to know about heating your hot tub including the reason why your hot tub is taking so long to get heated.

Let’s dive in.

If you want to use the hot tub, then you need to know how long does it take to heat a hot tub.

How Long Does It Take To Heat A Hot Tub For The First Time?

It takes between 4 and 5 hours to heat a hot tub for the first time. Most hot tubs get the water to 100 degrees Fahrenheit within 4 hours for the first time. The time it takes for a hot tub to get heated depends mainly on the temperature of the water coming from the tap.

Hot tubs generally take about 4 hours to get the water to 100 degrees Fahrenheit for the first time but the time it takes largely depends on the temperature of the water flowing through the tap.

On a warm day, the water temperature could already be about 80 degrees Fahrenheit. This means it would take your hot tub under 3 hours to get the water to 100 degrees Fahrenheit for the first time.

On a cool day, the water temperature can be about 60 degrees Fahrenheit or less. In this case, it would take the hot tub up to 4 hours to get the water to 100 degrees Fahrenheit for the first time.

But that’s not all. Several other factors affect the time it takes your hot tub to get heated. Let’s check out these factors below.

Factors That Affects The Time It Takes A Hot Tub To Get Heated?

Here are the factors that affect the time it takes your hot tub to get heated to 100 degrees Fahrenheit.

The Ambient Temperature

One of the things that affect the time to heat a hot tub is the ambient temperature. The higher the temperature is the faster the hot tub will heat, and vise versa.

The ambient temperature is the temperature around the hot tub. The ambient temperature is usually affected by the weather.

If the weather is cool, then the ambient temperature around the hot tub will be cool. This means it will take the hot tub a longer time to get the water heated to 100 degrees Fahrenheit.

However, if the weather is warm like it usually is during the summer, then the ambient temperature around the hot tub will be warm. This means the hot tub will get heated faster.

The Capacity Of The Heater

The heater size is also imporant. If the heat is more powerful and larger then the hot tub will heat faster.

The capacity of the heater determines how powerful the heater will be. If your hot tub was designed with a powerful heater, then you can expect the hot tub to get heated faster, usually less than 4 hours. But if the heater is not very powerful, then it can take over 5 hours for the water to get heated to 100 degrees Fahrenheit.

Hot Tub Insulation

Hot tubs usually have the inner walls and cover insulated to help the hot tub with heat retention. A well-insulated hot tub will heat the water faster because the heat produced by the heater is trapped inside the hot tub and used to heat the water.

However, if the hot tub is poorly insulated, then it will struggle to retain heat. A poorly insulated hot tub will also be easily affected by the cooler outer temperature. This means it will take longer to get the water heated to the needed temperature.

The Size Of The Hot Tub

The size of the hot tub also determines how long it takes to get the water heated. Larger hot tubs usually take longer to get the water as hot as 100 degrees Fahrenheit. This is because larger hot tubs usually contain more gallons of water. A 6 person hot tub for instance can contain over 600 gallons of water.

It will take over 4 hours to get this amount of water to 100 degrees Fahrenheit even if the hot tub was designed with a powerful heater.

Smaller hot tubs on the other hand get heated quicker because they don’t contain as much water as larger hot tubs. On average, it will take a 2-3 person hot tub just over 3 hours to get the water heated even for the first time.

The Set Temperature Of The Hot Tub

The temperature that you set your hot tub at determines how fast the water will get heated. A hot tub owner that sets his hot tub water temperature to 94 degrees Fahrenheit gets the hot tub heated faster compared to a hot tub owner that sets his hot tub temperature to 104 degrees.

Does A Hot Tub Heat Faster With The Jets On?

A hot tub heats faster when the jets are on because the jets help to eliminate any pocket of cold water in the hot tub through water circulation.

Jets are amazing features to any hot tub. The jets give increased hydrotherapy through gentle massages and muscle relief. But the jets also help to get the hot tub heated faster.

When the jets in the hot tub are on, there is increased water circulation in the hot tub. This is because the jets push out water and air at high pressure into the hot tub causing bubbles in the hot tub that circulate the water. This improved water circulation also helps to get the hot tub heated faster by ensuring that the water remains mixed.

The heater in the hot tub heats the water but the heater is only located in one part of the hot tub. This means the heater mainly heats the water around the area where it is located in the hot tub and it will take longer for the entire hot tub to get heated this way.

But when the jets are on, there is improved water circulation and the water gets heated evenly. The jets will also flush out cold water inside the hot tub’s pipes so the cold water can mix with the heated water. This also makes the hot tub get hot faster.

Related Read: Can You Run Hot Tub Jets With the Cover on?

Can You Start Heating A Hot Tub Before It Is Full?

You should not start to heat the hot tub water before the hot tub is full. Doing this will damage the whole hot tub system especially the jets. 

Since it takes a few hours for a hot tub to get heated, you may feel that you can get the water heated faster if you turn on the heater before the hot tub is full. This is a very bad idea because doing this will damage the hot tub jets and the entire system.

You may think that heating the water in the hot tub is only done by the heater. This is far from the truth. Though the heater is mainly responsible for getting the water hot, the hot tub gets heated through collective work by the hot tub components.

The jets and circulation pump keep the water circulated so it can get to the heater. If the hot tub isn’t full, this means that all the jets aren’t submerged in water. When the jets aren’t fully submerged in water, the jets will draw in dry air rather than water.

If the jets start to draw in air, it will lead to pockets of air being trapped inside the hot tub pipes. The trapped air in the hot tub pipes makes it difficult for water to reach the heater. When the heater doesn’t get enough water, it can burn out and hot tub heaters are expensive to replace.

So while turning on your heater before the hot tub is full might seem like a good idea, it’s not. It only starts a chain of actions that will eventually damage your hot tub’s components.

Related Read: How High Should You Fill Your Hot Tub?

How Long Does It Take For A Hot Tub To Heat Up To 10 Degrees?

On average, it takes a hot tub about 2 hours to heat up to 10 degrees. Most hot tubs are heated at a rate between 3 and 6 degrees per hour. So to get your hot tub heated up to 10 degrees, it will take the hot tub about 2 hours.

Hot tubs contain many gallons of water when filled. To get that amount of water heater up to 10 degrees usually take most hot tubs about 2 hours. Even with a powerful heater, it would still take over an hour for the hot tub to heat the water up to 10 degrees.

The time it takes for a hot tub to heat up to 10 degrees also depends on the capacity of the heater, the size of the hot tub, and the ambient temperature around the hot tub.

Related Read: Can You Fill Hot Tub With Hot Water?

Why Does My Hot Tub Take So Long To Heat Up?

Several reasons cause a hot tub to take so long to get heated. Some of the popular causes include a damaged heater, cold ambient temperature, and low water level. Let’s check out these factors in detail and how to troubleshoot them.

A Damaged Heater

If your hot tub is taking too long to get heated, the culprit is usually a damaged heater. When the heating mechanism of the hot tub gets damaged, the water wouldn’t get heated as fast as it should. Sometimes, the water wouldn’t even get heated at all.

The heater can get damaged as a result of low water level, too much use, or hot tub scale.

Low Water Level

Another reason your hot tub is taking so long to get heated could be a low water level. When the water level in the hot tub is below the required height, there will be low water flow in the hot tub. When the water flow is low, the heater wouldn’t get enough water and this can cause the hot tub to take very long to get heated.

Cold Ambient Temperature

The ambient temperature refers to the air temperature around your hot tub. The ambient temperature is usually affected by the weather.

When the weather is cold like it is during winter, it can take very long for your hot tub to get heated. This is because the ambient temperature around the hot tub is causing the water in the hot tub to get cool too. So your hot tub heater has to work twice as hard to heat the water.

A Faulty Temperature Sensor

If you have a modern hot tub, a faulty temperature sensor could be the reason your hot tub is taking so long to get heated. Modern hot tubs are usually designed with a temperature sensor that monitors the water temperature in the hot tub. When the water gets too hot, the temperature sensors are triggered to automatically turn off the heater.

If the temperature sensors are faulty, they could be interfering with the heater by turning it off even when the water isn’t hot enough.

Related Read: Why is Your Hot Tub Not Heating Up?

What Temperature Should A Hot Tub Be Set At?

A hot tub temperature should be set between 100 degrees and 104 degrees Fahrenheit. Most hot tub users discover that water temperature within this range offers the best comfort and relaxation.

There isn’t a specific temperature to set a hot tub at. The temperature of the hot tub depends on what the user wants. You can test out different hot tub temperatures while soaking in your hot tub to find out which works for you.

Final Words

Overall, hot tubs take a while to get heated due to several reasons. But you can speed up the heating time of your hot tub by providing better insulation, using the jets, and keeping the hot tub cover on.

So there you have it. If you liked this post, ensure to check out others like it on this website for more hot tub tips. Have a nice day.

Hi, I'm Calvin Hall, the owner of Hot Tub Wiki. I worked at a local Spa Service for a few years before creating this website. I have owned several hot tubs and fixed a thousand of them. So, I know a thing or two about hot tubs.