How to Heat a Hot Tub Using Solar Energy

A Guide to the Heating of Hot Tubs by Solar Means

Solar heat for your hot tub? Not just a bright idea  it’s obvious!

If you’re fed up seeing your energy bills soar every time you fancy a soak, that makes sense. We have heard it from many of our customers.

Bubbling hot bubble baths: There’s nothing like it for wallowing in warm luxury, if you can afford to heat several hundred gallons of water past 100 degrees.

Having worked with families, resorts and spas across the USA, UK and Europe 

The problem I hear most frequently is:

“It’s like the same price as just keeping the water warm.”

So, guess what? There’s an easier way.

No gas. No huge energy bills. Just clean solar heat.

And today it’s all about heating your hot tub with solar  without making things more complicated than they should be

Benefits of Using Solar Heating For Your Hot Tub

So this may be what’s happened and why you’ve arrived here.

You invested in a hot tub to chill out.

To not have to worry about monthly operational fees.

Solar water heating is the process of heating water using a solar thermal system. You literally get heat from the sun  not from your mains electricity or gas. That would lead to reduced emissions and smaller bills.

What’s better?

Covered on sunny days (that’s when you’ll probably want to use your hot tub) and your system’s pumping out free heat.

Why it is good for hot tubs?

• Most hot tubs do not require boiling water, just warm water for comfort.
• They can range from 200 litres up to 1,000 litres  the ideal size range for a residential solar hot water system.
• A lot of them are already on flat roofs, or people have open patios, which are great places for hot water solar panels.

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What Is Solar Thermal or Solar Hot Water System?

Let’s break it down simply.

With a solar thermal system, heat is created from the sun, which is absorbed in a collector (yes, that’s the thing that looks like a mini sun bed for water).

It works like this:

1. Sunlight strikes the solar collector  which is a flat plate, evacuated tube, or prismatic collector design.
2. The collector heats water or a heat transfer fluid within it
3. That heat travels in pipes to your hot tub (typically through a solar energy water heater tank or a regular pump)

The best bit?

It’s simple, silent, and low-maintenance.

Comparison of various solar heating solutions for tub water heating

At SolarisKit, we’ve spent six years testing different kinds of solar hot water heaters in some of the world’s least forgiving climates  Rwanda, Kenya, Dubai, even hard water zones in the U.K.

Here’s what I’ve seen:

Flat-plate solar panels

1. Inexpensive and easy, but looking into them they do tend to get too hot in warmer climates
2. Not Ideal For Hard Waters  The minerals can gunk up copper pipes
3. Non-modular  no easy to move/fix parts and is actually quite large. You likely wouldn’t want to get one installed next to your hot tub.

An example of how a flat plate solar thermal system looks.

Evacuated tube collectors

1. Great insulation, but fragile
2. Breakable, especially on roofs
3. Often bulky and hard to clean

HelioFlow by SolarisKit (yes it’s ours  and here’s why I’m supporting it)

We designed HelioFlow specifically for:

• Flat and roof or ground installations (most hot tubs are placed in very open spaces)
• In hard water systems (using a scaling-resistant polymer tubing)
• No overheating  it doesn’t cool you or your tub on a hot summer day

It ships flat-packed and is very easy to install, and offers a design influenced by the cubic design trend so it’s less cluttered and looks more modern than the regular old silver tubes or clunky boxes.

I’ve seem it do a good job on a 500L hot tub in Dundee Scotland, which was able to maintain 37–40C during sunny spells with a tiny 12VDC (less than 15W draw iirc) circulation pump!

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How to Install a Solar Hot Water System for a Hot Tub

You don’t have to tear up your garden or drill into your roof.

Here is how you can set up something simple:

The Install Process is as follows:

• Position and mount the solar panels. We’d suggest to keep the solar collectors within 10m of the tub or so, to keep heat losses, and pumping power, to a minimum.
• Plumb the hot tub and solar collectors. Below we have a step-by-step video which takes you through the entire process of fitting our HelioSpa solar heating kit.
• Join the pump and the wire to the pump controller. An automatic control of complete heating is exercised by the pump controller.
• Hook up temperature sensors (usually 2) to the controller so it can read the temperature of your hot tub and your solar collectors.
• Turn on the controller and begin drawing energy from the sun!

Basic equipment checklist:

 

• Solar collector (like HelioFlow)
• Pump (DC or AC & Controller)
• Piping (insulated for heat loss)
• Pump Temperature control (for all model, To avoid Over Hitting).