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How to Heat Up a Hot Tub Faster – 17 Proven Hacks

By: Author Jeff Campbell

Posted on  - Last updated:

Categories Hot Tub Operational Tips

We all know the feeling. You just filled up the hot tub, and now it’s taking ages to heat up. You keep checking the hot tub and at best it feels lukewarm, leaving you wondering how to heat up a hot tub faster.

Here are some of the best ways to heat up a hot tub faster:

  1. Preheat the water: Before using the hot tub, fill it with hot water from another source, such as a hose connected to a hot water tap. This initial hot water will help to reduce the time it takes for the tub to reach the desired temperature.
  2. Use a well-fitting hot tub cover: Always keep the hot tub covered when it’s not in use. A high-quality cover will help to retain heat and prevent heat loss, allowing the tub to heat up faster and more efficiently.
  3. Ensure proper insulation: Insulate the hot tub properly to minimize heat loss. This includes insulating the sides, bottom, and plumbing lines of the tub. Good insulation will help to retain heat and speed up the heating process.
  4. Adjust the jets: Turn on the jets in the hot tub to circulate the water after a refill. This will help to distribute the heat evenly and speed up the heating process. Ensure that the jets are adjusted to create maximum water movement for optimal heat distribution.
  5. Use a thermal blanket: Consider using a thermal blanket specifically designed for hot tubs. This floating blanket sits on the water’s surface and acts as an additional insulation layer, reducing heat loss and helping the tub heat up faster.

But those are only 5 of my 17 tips!

You’ll be pleased to know that there are lots of things you can you to speed up the heating process in your hot tub with no cost to you. In fact, some can actually save you money!

So, to learn my 17 hacks for heating your hot tub quicker, let’s dive in!

Here we go, in no particular order.

heat hot tub faster lg

Now let’s review the . . . 

17 Proven Hacks to Heat Your Hot Tub Faster

1. Leave the cover on

If you leave the cover off while your hot tub water is heating up, you will lose a lot of heat through evaporation. Even indoors, the temperature of the water in your tub will be much higher than the ambient air temperature, so you’re always going to get a transfer of heat to the lower air temperature.

This principle applies no matter what type of cover you have or how well-insulated it is. Heat is lost through evaporation, so stop that, and your hot tub will heat up quicker.

2. Keep the jets running

The jets use what is known as a Venturi effect to create bubbles. By narrowing the diameter of the pipe at the jet, the pressure increases, and this, in turn, raises the temperature of the water coming out.

Running the jets also moves the water around in the tub, getting into all the corners where cold water can sit, bringing the overall temperature down.

Most jets time out every 15 minutes or so, so just turn them back on as needed.

3. Use a thermal cover

All hot tubs lose heat to evaporation.

And when you’re heating your water temperature back up after changing the water, every degree counts! So trap the heat in the water as the heater goes to work by floating one of these on the surface of the water.

A thermal spa blanket used in addition to a well-fitted and insulated hot tub cover will keep more heat in and let less heat out. These are inexpensive and can be cut to size with scissors easily if need be.

CLICK HERE to see my favorite one on Amazon.

4. Keep your hot tub under a gazebo

Positioning your hot tub under a gazebo or a similar structure will provide shade on those really hot days, and it will also help keep the heat in on a cooler day.

Gazebos come in all shapes and sizes. It can be a permanent wooden frame with a shingled roof or a metal framed pop-up. They are all effective at regulating the temperature and enabling the water to heat up quicker by reducing evaporation.

Want some good ideas on DIY gazebos and privacy structures? Check out my recent article where I go through all the best ways to do that on a budget.

Just click that link to read it on my site.

5. Do it on a hot day – or the hottest time of day

Filling up your hot tub late morning will give you the afternoon – the hottest part of the day – to allow the water to get up to optimum temperature.

Air temperature is one of the main factors in determining how long it takes for the water in your tub to heat up. Timing the cleaning and water change cycle at the hottest times of the year will help you get the job done a lot quicker.

So, if you change the water every 3 months, make that April, July, and October. If you overwinter your tub, October should be the last time you empty your tub, and it can be left then until the following spring.

6. Use warm water to fill up

Using pre-heated water from the faucet to fill your tub is something often frowned upon, but it can be effective in getting the water up to the required temperature in half the time.

If you intend to use this technique, don’t just run a hose from your hot water heater. You don’t want water at 130⁰ running through your pipes!

But if you can attach a hose to a kitchen faucet and run warm-ish water through it to the hot tub, you’ll save hours in your hot tub heating.

7. Use a portable immersion heater

A portable heater that can be immersed in the water will help boost the heating process.

The Philex electric immersion heater on Amazon provides 1.5kW of power, and it is suitable for inflatable hot tubs too. Take a look at this on Amazon by clicking on the link.

At less than $30, a portable immersion heater is an economical way of improving the water heating time by up to 50% when used in conjunction with your built-in heater.

8. Use an in-line water heater

If you fill your hot tub through the garden hose, you might consider connecting it to an in-line water heater such as the American Standard Safe-T heater on Amazon – just click on the link for the latest price and availability.

This 1.5kW heater has a cut-out to prevent it from getting too hot to cause damage to your hot tub or equipment, and like the immersion heater, when combined with the built-in heater, it can halve the time it takes to get to 100⁰.

9. Keep your hot tub in a shielded area

Wind can really chill the water, slowing down the heating process, so if you can shield your tub by using fencing or a wall on the prevailing wind side, you can knock a good 30 minutes off the time.

Shielding can also be achieved using plants. One of the best types of tree for this purpose is the willow, but if you’re looking for something a bit smaller, leylandii grown in containers make an excellent windbreak.

Avoid trees that shed leaves in the fall or blossom in the spring.

10. Turn the thermostat down

If you can reduce the hot tub’s water temperature by 5⁰, this will knock at least an hour off the time it takes to get to your desired temperature.

In the summertime, you might find that 100⁰ is too hot, and you feel more 95⁰ or even less is a more comfortable temperature, depending on the ambient temperature at the time.

11. Leave the hot tub on all the time

When you turn off your hot tub, it will start to cool down fairly quickly, so when you next come to use it, you’ll have to wait while the water heats up enough. It’s always best to leave the heater running all the time, even if only in standby mode.

Don’t worry about energy costs. The average cost of running a hot tub is around $1/day, maybe $1.20 for an inflatable hot tub. However, the bulk of this cost is in raising the temperature to 100⁰ – keeping it there is relatively cheap and the most efficient way of heating it.

Leaving your hot tub on also means that it is always ready for that impromptu moment when you just feel like a good soak.

12. Make sure everything’s working efficiently – clean the filters

Filters serve to capture all the waste products from using a hot tub – the dead skin, body lotions, perfume, and hair. These build up to form a biofilm that clings to the inside of the pipework and pump.

A clogged or dirty filter will not be able to pull as much water through it and into the heater as a clean filter will.

You should remove and clean your filter at least every 3 weeks.

I recommend the Filter Flosser from Amazon, which connects to your garden hose and helps you get right into those folds. Check it out here on Amazon by clicking on the link.

Every 3 or 4 months, you will need to give your filter a deep clean by soaking it in a cleaning solution such as Spa Depot’s Power Soak from Amazon and water. This removes the waste products, and it also contains enzymes to eat up organic contaminants.

13. Keep the water clean and healthy

If you get a build-up of biofilm or scale build-up in your pipes, this will reduce the flow of water and slow down the heating process.

Keep the water clean by regularly:

  • checking the pH and alkalinity levels  
  • adding sanitizer – chlorine or bromine
  • shocking your hot tub using chlorine or non-chlorine shock 
  • changing the water and thoroughly cleaning your hot tub every 3 months

This, together with cleaning the filters, will keep the water flowing freely and help heat the water faster.

Every time I change my water, I use 8oz of Oh Yuk! Healthy Hot Tub Cleaner from Amazon. It helps ensure there is no biofilm buildup. And when I refill, my new water is as clean as possible.

14. Increase the size of your heater

Upgrading your heater from a 4kW to a 6kW will give you a 50% increase in power, reducing the amount of time it takes to get your water up to 100° by around 25%. So, if it took 8 hours with a 4kW heater, it would take 6 hours with a 6kW heater.

Many hot tubs can be upgraded except for inflatables and other plug-‘n’-play types. These are limited by the plug connection and usually come with a 1kW heater.

15. Change the type of heater 

You don’t have to rely on the built-in heater to raise the temperature of the water in your hot tub. This may seem radical, but there are a host of fuel sources available to help heat your water quicker and save money.

One I recently came across is by using a heat exchanger in conjunction with a conventional heater to raise the temperature by as much as 54⁰ per hour. You can find more information on the Bowman heat exchanger on their website.

Heating the water using natural gas can raise the temperature at a rate of 1⁰ per minute. Sounds good, but this is only a viable option if you have a gas supply to your home.

Using a wood burner or, better still, a rocket stove to heat your water is a great way to get you up to 100⁰ in just a couple of hours. The downside is you need to install flow and return pipes in your hot tub.

16. Increase insulation to keep the heat in

Luxury hot tubs are usually well insulated, but for most of us with mid-range hot tubs, there’s always room for improvement, up to a point.

The first thing to check is the cover.

The best covers in terms of insulation contain closed-cell foam with a density of 1.5 to 2 pounds per square inch (the higher the density, the better). The foam is usually tapered to allow rain to run off.

Typically, a 6” foam will taper down to 4”, so this is what you should aim for.

It’s also a good idea to use an insulated mat beneath the tub will prevent heat from escaping to the ground. About 25% of the heat can be lost this way, even more with an inflatable tub.

Adding insulation to the cabinet can help reduce heat loss and reduce noise too!

Polystyrene fixed to the walls of the cabinet is a good way to achieve this, but be careful not to block any ventilation slots.

Most heat is lost through the pipes, pump, and heater, so adding insulation here will help. Touch ‘n’ Foam from Amazon is a good spray foam for insulating pipes and hard-to-reach places.

17. Ship your water pre-treated and pre-heated

This might not be an option for everyone, but many pool owners do this if their tap water isn’t suitable or they have to fill from a well.

The advantage of doing this is that the water is already balanced and sanitized, and the temperature will be no more than 100⁰F, so it won’t damage your tub or the electrics.

The downside is this will be expensive as most suppliers will only deliver minimum quantities of 2,000 gallons for a pool refill.

Frequently Asked Questions

How long does it take for a hot tub to warm up?

On average, it takes about 6-8 hours to heat your hot tub to around 100°F, which is the optimal temperature for most people. Some like it hotter, but the maximum is 104⁰ F, and the minimum for comfort is around 98⁰.

The temperature of the water from the hose is the biggest factor as it can range from 60-75⁰ F. You can speed this up by using warm-hot water from the faucet of a nearby sink if you have a hose attachment on it.

But there are two things to consider before doing this. First, avoid filling directly from the hot water heater. The temperature of the water will be more than 130⁰ – way too hot for you to get in, and it could damage your plumbing, equipment, and the shell.

You can read more about this in a recent article here on my website by clicking on the link.

The other consideration is a chemical imbalance. If you live in a hard water area, chances are you have a water softener attached to your supply.

Softened water can lead to corrosion of the pipes and equipment, so you need to disconnect this if using water from the faucet. Or you can add some Leisure Time Calcium Booster from Amazon.

Should jets be on when heating a hot tub? 

As a rule, water heats up quicker with all the hot tub jets and water features on. That’s because it circulates all the water through the heater and filter system which eliminates pockets of cold water. So it’s the fastest way to maximize the efficiency of your hot tub.

So turn them on, keep the lid closed and every 15 minutes or so, lift the lid just long enough to restart the jets, as they typically time out after 15 minutes.

But there are exceptions to this.

If you have an inflatable or another type of plug ‘n’ play hot tub, you will most likely find that you can’t run the jets and the heater at the same time.

This is because these spas run off a 110v supply, and that’s not enough to run the jets and heater together. Plus the heater has a much lower wattage heating element, so even with the jets off it can take 2-3 times as long to heat up.

Most regular hot tubs are hard-wired through a disconnect box to the 240v supply to your home, which means you can leave your jets running while you’re heating the water.

The benefit of leaving the jets on is that by circulating the water, you prevent cold pockets from appearing in the corners of your tub. Also, the effect of forcing the water through the pipes and jet nozzles heats the water through friction.

How long does it take to heat up a hot tub outside?

Water in a typical hard-sided 220v hot tub typically heats between 4-6 degrees per hour. So if the hose water is 70° F and the set temperature is 100° F, the total heating time would be between 5 and 7.5 hours.

In a recent article, I went through the factors affecting the length of time it took to heat a hot tub. Just click on the link to read it here on my website, but here are the main factors:

  • The current temperature of the hose water (can range between 60°-75° F)
  • The weather conditions at the time (winter can make it take a lot longer)
  • The amount of water in your rub
  • The size of your heater

Depending on the above factors, it can take anything between 4 and 48 hours to get the water in your tub up to the optimum temperature of around 100⁰.

The smaller plug-n-play hot tubs can take four hours to heat up by just 5°, which is why many people regard these as summertime spas.

This is due mainly to the size of the heater, but they can be used all year round if the conditions are right.

Weather plays a major part in the time it takes to heat the water; Air temperature and wind chill in particular. Leaving the cover off on a windy day will cool the water down almost as quickly as the heater warms it up, and on cooler days, it will take longer.

Final thoughts

I gave you hot tub owners 17 hacks there to think about, some of you probably knew already, but I hope you learned some new tricks as well. In most cases, getting your hot tub to heat up faster will be a combination of a number of these things.

If there is anything I missed or you have any questions on this subject, just drop me a line, and I will do my best to answer it. And don’t forget to check out the other related articles here on my site.

Just click on the links.

Image by OpenClipart-Vectors from Pixabay and Image by Sawan Juggessur from Pixabay

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Jeff Campbell
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