How Long Does It Take to Heat Up a Hot Tub? | Hydropool Midlands

One of the most relaxing experiences you can have at home is slipping into your warm, soothing hot tub. But there’s nothing worse than looking out to see the hot tub isn’t at the right temperature, and the dreaded question begins to loom, "How long will it take to heat up this hot tub?" 


In general, a hot tub can take anywhere from 3-8 hours to heat up, heating up at a rate between 2 and 7 degrees celsius every hour. Several factors, such as the starting temperature of the hot tub, the surrounding environment temperature, the quality of the hot tub and its components, all have an effect on the time it takes for the  hot tub to heat up.


Let’s investigate these factors in more detail, so you can optimise your spa to heat up as quickly as possible.

Factors that influence the rate the hot tub heats up

The Starting and Desired Temperatures

The time required to heat up a hot tub is highly influenced by both the starting water temperature and the desired temperature.


On average, a hot tub can heat up at a rate of 2-7 degrees Celsius per hour. If your water starts at 15 degrees Celsius and you want it to heat up to 40 degrees Celsius (the recommended maximum), it could take anywhere between 4 and 12 hours. However, if the water is already at a higher starting temperature, such as 30 degrees Celsius, the heating time would be reduced to between 2 and 5 hours.


The higher the starting temperature, the less time it will take to reach your desired temperature. Conversely, starting with a lower temperature will extend the heating time. 


Depending on how frequently you use the spa, it can be more energy efficient to keep the hot tub at a constant higher temperature, rather than heating it up from cold before every use.

Environmental Temperature

The ambient or environmental temperature is perhaps the most important factor in how quickly a hot tub can heat up. 


If you have your hot tub outside, the colder weather will cause the water to lose heat more rapidly. This requires the heater to work harder to maintain the desired temperature. The difference can be substantial, with heating times in summer typically ranging from 2-5 hours, compared to 3-8 hours in winter.


Ensuring that your hot tub is well-protected from cold environmental temperatures is vital. This protection can be achieved by making the hot tub more 'weatherproof,' utilising insulation covers, and implementing other insulating measures such as windbreaks and thermal blankets.


An alternative solution is to place the hot tub in a more constant warmer temperature environment, such as indoors. While this option isn't viable for everyone, it eliminates the impact of outdoor weather conditions, providing consistent heating times year-round.

The Power of the Heater

The heater is the heart of a hot tub's heating system. Typically, hot tub heaters come in two main varieties: electric (the more common variety) and gas. Generally, the higher the power of the heater, the more energy is transferred to the water in a shorter amount of time, heating up the tub more quickly.


If you’re looking to drastically increase the amount of time your hot tub heats up, upgrading your heater can be a great option.

Hot Tub Volume

The volume of the hot tub, or how much water it holds, also directly influences the heating time. A larger hot tub with a capacity of around 2,000 litres will take longer to heat because there is more water that requires energy to raise its temperature. In comparison, a smaller one that holds around 1,000 litres of water will need less energy, and thus less time, to reach the same temperature, assuming they use the same heater.


The level of insulation affects the heating time of your spa significantly. High-quality insulation traps the heat inside, keeping the hot tub warm for a more extended period. This reduces the need for the heater to work continuously, thus conserving energy.


Examples of insulation methods include

Full-Foam Insulation: 

Full-foam insulation fills the entire cabinet with a high-density foam. This method provides excellent insulation and also adds structural support to the hot tub.

Thermal Blankets: 

These specially designed blankets float on the water surface, reducing evaporation and heat loss. They are a great additional layer of insulation, especially when combined with a quality cover.

Insulating Hot Tub Covers:

Heavy-duty covers with a high R-value (thermal resistance) can greatly reduce heat loss when the tub is not in use. Look for covers with a tapered design that allows water to run off, and a thick layer of foam for maximum insulation.

Perimeter Insulation: 

This method insulates the shell of the hot tub but leaves the space under the tub open so that the generated heat from the pumps helps warm the water. It’s a less expensive insulation method compared to full-foam insulation.

Reflective Insulation: 

Also known as radiant barriers, reflective insulation consists of reflective materials that reduce heat transfer by reflecting radiant heat away from the water. This can be used on the inner walls of the hot tub enclosure.

Base Insulation: 

Insulating the base of the hot tub can prevent cold from seeping up from the ground. This might include placing a thermal pad beneath the hot tub.

Insulated Spa Jackets and Skirting: 

These wrap around the exterior of the hot tub, providing an extra layer of protection against the elements.


While not insulation in the traditional sense, windbreaks like fencing, landscaping, or outdoor screens can reduce the wind chill effect on the hot tub, thereby slowing heat loss.

Using a Combination of Methods: 

Often, a combination of these methods will provide the best insulation. Working with a professional to evaluate your specific hot tub, location, and climate can help you determine the most effective insulation strategy.


Remember, proper insulation not only helps to keep the hot tub warm but also significantly reduces energy consumption, making your hot tub more economical to run. These methods vary in cost, effectiveness, and installation complexity, so it might be wise to consult with a hot tub professional to determine what will work best for your specific needs and environment.


Lastly, the condition and maintenance of your hot tub greatly influence its heating time. A well-maintained hot tub with clean filters and a functioning heater will heat more efficiently. Clean filters allow better water flow, and an efficiently functioning heater converts energy to heat more effectively.


On the other hand, neglected maintenance may lead to clogs, reduced water flow, and a less efficient heater. These factors force the heating system to work harder and longer to achieve the desired temperature, resulting in longer heating times and less efficient use of energy.


By understanding and carefully managing these factors, one can optimise the heating time of a hot tub, making it more energy-efficient and ready for use in a shorter amount of time.

How to Heat Up Your Hot Tub Faster

Use a Higher Powered Heater:

Consider using a heater with a higher kilowatt rating for your spa. A heater with a higher kW rating will heat the water faster than a lower-rated one. 

Maintain Your Hot Tub:

Ensure that your hot tub is regularly maintained. Clean the filters and ensure that the heater is in good working condition, as well as getting your hot tub serviced once a year. A well-maintained hot tub will heat up more quickly and efficiently.

Upgrade the Insulation:

Improving your hot tub's insulation will retain more heat and reduce the time it takes to warm up. Consider investing in a high-quality, well-insulated cover that fits snugly over your tub to help hold the heat in when it's not in use. Check out the selection of hot tub enclosures at Hydropool Midlands, designed to retain heat and save energy.

Start with Warm Water:

Filling your hot tub with warm or hot water to begin with can significantly cut down the heating time. The heater won't have to work as hard or long to bring the water temperature up.

Block the Wind:

Wind can cool down your hot tub and slow the heating process. Use a windbreak like a fence or outdoor screen to protect your hot tub from the wind.

Use a Preheater or Solar Cover:

Solar covers or preheaters can also help speed up the heating process. Solar covers can harness the power of the sun to raise the water temperature, while a preheater can heat the water before it enters the tub. Hydropool Midlands offers energy-efficient solutions to help you reduce heating times and enjoy your hot tub sooner.

Use the Jet Mode Less:

Running the jets can cool down the water as it introduces cooler air into the tub. Use this feature sparingly if you want to maintain the hot temperature.


Remember, safety should be your first priority when dealing with electrical appliances and water. Always hire a professional to install or service your hot tub heater, and never exceed the recommended maximum temperature of 40 degrees Celsius.

Bonus Tip:

If you use your hot tub frequently (around 3 times a week), it may be more energy-efficient to keep the heater set to a consistent temperature. This approach can reduce energy consumption and costs, as it's more efficient than letting the water cool and reheating it each time. Keeping the water at a desired temperature ensures that the hot tub is always ready for use and eliminates the waiting time for heating from cold.

Ideal Temperature for a Hot Tub

The ideal temperature for a hot tub is largely a matter of personal comfort, but there are some recommended guidelines to ensure safety and optimal enjoyment.


According to the BISHTA (The British and Irish Spa and Hot Tub Association), the water temperature of a hot tub should never exceed 40 degrees Celsius. Bathing in water hotter than this can lead to heat-related illnesses like heat stroke, especially with prolonged exposure.


Most hot tub users find a temperature between 37 and 38 degrees Celsius to be comfortable. This range offers a warm, relaxing experience without posing as much risk for heat-related health problems.


If you're using the hot tub for therapeutic purposes such as recovery from physical activity, a higher temperature closer to the 40 degrees Celsius mark may be more beneficial, though it's essential to limit your time at these higher temperatures.


For pregnant women, it's recommended to consult a healthcare provider before using a hot tub.


Remember, the above temperatures are guidelines and can depend on individual health conditions, age, and personal comfort levels. Always follow the advice of health and safety professionals when determining the appropriate hot tub temperature for you.


In conclusion, the time it takes to heat up a hot tub is influenced by various interconnected factors. From the starting and desired temperatures to the heater's power, hot tub volume, insulation quality, environmental conditions, and regular maintenance, each aspect plays a significant role in determining the heating time. Understanding these factors and employing methods such as maintaining a constant temperature can save both time and energy.


For those seeking an optimal hot tub experience, it's worth considering brands known for quality and efficiency. Hydropool, for example, offers hot tubs designed with innovative technology that caters to these heating factors, ensuring a quick and energy-efficient heating process; we can even build you a pool room for your perfect hot tub environment.  Don’t hesitate to get in touch with us or visit one of our showrooms for more information.


Why does it take so long to heat up a hot tub?

Hot tubs take time to heat up due to the large volume of water they hold, limited heating capacity of the heaters, insulation to retain heat, safety considerations, and the impact of environmental factors.

Are there any tips to make the hot tub heating process more cost-effective?

To make the heating process more cost-effective, consider using a timer to schedule heating during off-peak electricity hours. Additionally, invest in a well-insulated hot tub cover to minimise heat loss.

Can I use my hot tub while it's heating up?

It is generally not advisable to use the hot tub while it's actively heating up, as the water might not be at the desired temperature yet. It's best to wait until the hot tub reaches the desired temperature for a safe and enjoyable experience.