Solar Powered Hot Tubs: What you Need to Know

Due to the rise in the effectiveness of solar thermal panels, it has become more popular to heat hot tubs using solar energy. The essential idea of a solar hot tub is to use solar collectors during daylight hours to heat the hot tub.

We do recommend you keep your existing heater and run the solar system on a secondary loop because in the evening you may still need to use a backup heater.

Solar Powered Hot Tubs: What you Need to Know

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Advantages of a Solar-Powered Hot Tub

While it is certainly more environmentally friendly to have a solar powered hot tub, it will also end up saving you money. The various elements needed to set up your solar-powered hot tub are relatively inexpensive. The equipment is also fairly easy to install; you don’t even need to hire a professional to install it.

Furthermore, you will save money over the long term with solar because alternative heating methods for a hot tub can be less cost effective. Another advantage is that once you have installed or upgraded these elements of your hot tub to enable solar efficiency, the system will not require regular maintenance for many years to come.

Moreover, for the environmentally friendly person, solar energy is the way to go. Not only does it reduce your pollution output, but it also lowers your overall carbon footprint.

How to heat up your hot tub using solar energy?

If you live in an area that gets around 6 hours per day of strong sunlight, then this technology will be very effective. All you will require is a heat exchanging panel.

To put it simply, cold water will exit through the bottom of your hot tub and will then pass through the heat exchanger. The heat exchanging panel is crisscrossed with small tubes set against a black background, through which the water passes. Usually there is a glass or Perspex layer over the front; this acts to amplify the heat.

The sun heats up the cold water as it passes through the small tubes and out the other end of the exchanger. This heated up water is then piped into the top part of the hot tub. When the water starts to cool it will drop lower down the tub and will then pass through the system to be warmed up again.

Installing a Solar Hot Tub Heater

1. Locating the Solar Panels: Step one is to decide where and how you are going to mount your solar panels. If you have full sun throughout the day, you could lay them directly on the ground. Most folks find that mounting them on a roof or a rack at a 30-45° angle works best. You can build a rack using angle iron or lumber and top it off with plywood or plastic, then paint it black.

An alternative is to hang your panels on a fence. Whatever you decide, make sure you choose a spot that will get a minimum of 6 hours of sun a day; a southern facing direction often works best.

2. Buying the solar panel: For most hot tubs a single 4′ x 20′ solar panel, a total of 80 square feet, is a good size. The alternative is the 4′ x 10′ panel, but these are priced higher per square foot.

One 4′ x 20′ solar panel is sufficient to heat up a tub with under 500 gallons of water to over 100° during the day and be ready for the evening. In order to heat up your hot tub in under an hour like my friend likes to do for his pool/spa, you will need 4-5 of the 20′ panels.

3. Installing your Hot Tub Solar Panels: The panels consist of polypropylene mats made up of small black tubes with a continuous backing, to absorb more heat than the black hose DIY solar spa heaters.

The package includes two 2’x20′ solar panels, pipe adapters, end caps, a mounting kit and a 3-way diverter valve. Ensure that you fix the panels securely to your chosen location. They should be protected from high winds, tree branches and animals. Once secured, attach the end caps, and then run the PVC pipe from the panels to the plumbing line of your spa.

4. Installing the plumbing: Once you have run the PVC pipe from the solar panels to the hot tub, a 3-way diverter valve will allow you to adjust the flow rate or to shut off the solar panels completely.

In addition to the pipe, you will need the following items to complete the plumbing. Directional fittings (90’s or 45’s), couplings to connect the pipes and a check valve installed just before the heated water returns into the spa plumbing, to prevent any water cycling.


Choosing to install a solar heating for your hot tub is dependent on a few factors: the amount of use your tub gets, the amount of solar heat available in your area, and finally your personal environmental goals.

Our opinion is that it would be difficult to recoup the cost of installing a water heating solar system because you will most likely not be able to have it fitted until your tub is out of warranty.

This will limit the number of years you will have to recoup the cost.

But this may not be the case if you live in a very sunny part of the world and if you do not use your hot tub too often. Over time, this type of heating system can save you a lot of money if your current energy costs are high.

If my tub was older and out of warranty, I would be tempted to install a solar heating system as above. As long as you are willing to make some small changes to your hot tub, the temptation of free water heating is great.

A battery system may be well worth looking into if you don’t want your warranty to be affected. It offers a much longer time to recoup your money. You will require a specialist to help you determine the correct specs depending on your particular circumstances.

Finally, think about adding solar power to your hot tub as part of embarking on a wider solar conversion for your entire house. While we are only on the edge of exploring how this type of renewable energy is financially viable, many governments are offering conversion grants currently as incentives.

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