5 Considerations Before you Install an Air Source Heat Pump on your Hot Tub

Air Source Heat Pump

Installing an Air Source Heat Pump to your hot tub is a great way of saving money on your running costs. In this current climate, electricity prices have soared over recent months. Running your Hot Tub on electric alone is not economically viable for most of us.

If you have found this article as you are considering adding an Air Source heat Pump to your hot tub, then read on. I will cover the 5 key considerations before you make the decision and take the plunge to cheaper running costs of your tub.

In this article I am not going to cover how to install an Air Source Heat Pump as I have a much more complete article here. I want to look at in detail the 5 considerations as I see them.

Is Your Hot Tub Under Warranty?

Why is this important I hear you ask. Well, the moment that you cut into a pipe or make a hole in the cabinet, the chances are you are going to invalidate your warranty. A manufacturer will have a clause in their warranty document that states you may not modify the tub in any way. If you do, you will invalidate the warranty.

What is my take on this? Well, I guess as I am a little different as I design these for a living. However, what I would say is that if you are comfortable in adding an air source to your hot tub, they you can service it yourself too. You don’t need the warranty!

Also, what I have seen is that any of the parts that fail, generally will not be covered under warranty anyway as they will have at some point generally had water in them. This means the manufacturer will deem this outside of regular use anyway.

Pump fails as the coil has rusted – water where is should not be.

Blower fails and is tripping the breaker – water where it should not be.

These would not be covered by most manufacturer’s warranties.

There are lots of ways the manufacturer will wriggle out of a warranty claim so I’d so go for it – you might as well start saving the money on your running costs. (This is just my opinion so please make up your own mind whether you are comfortable going out of your Tub’s warranty)

What Size Air Source Heat Pump Do I Need?

This is a great question and one I get asked a lot. As a general rule, bigger is better and bigger means faster heat up times. As another general rule, bigger does not necessarily mean more economical. I will cover the COP or Coefficient of Performance below, but most ranges of Air Source Heat Pumps have the same COP rating right across the range.

Therefore, my general guide is as follows.

Install as big of an Air Source as your budget can afford.

If you have around a 1000L to 1500L (265-400 Gallons) – smallest size should be 7KW

If you have 1500L to 2000L (400–528 Gallons)  smallest size should be 9KW

2000L-2500L (528-660 Gallons) – smallest size should be 12-13KW.

This covers most plastic shell hot tubs.

What Specifications Should I look for?

As I have already mentioned above, the COP or the Coefficient of Performance is one of the key numbers you are going to look for.

This is a measure of efficiency and it will tell you how much heat you are going to get out versus what amount of electricity you are going to have to put in to generate that.

For example, a COP of 6 means for every 1KW in you get 6KW out – pretty straight forward. Now, I’ve seen lots of COP number banded around by different manufacturers. Something from 5-10 is good – personally I question those outside of this number. Again, this is only my personal opinion of course but I would say look for something between 5 and 10.

The next specification tends to be the running or operating temperatures. These again you should take with a pinch of salt but you must of course be mindful of your ambient temperatures during the colder months.

If you live in an area that can go for days at sub 30s (0C) then you definitely need a heat pump that is rated into the late 20s (-5c) If you live in somewhere like the UK, that doesn’t spend much of the time sub zero then having a -15C (5F) rated air source heat pump is an overkill – it is just not needed.

The common misconception here is that just because an Air Source Heat Pump is not rated to sub zero it will stop working – that is not the case. If you read the small print on a manufacturer’s manual, they will state they cannot guarantee the stated COP at less than those temperatures. Worst case, you get a COP of 1 – just like if you were running on an electric heater.

I have access to all of the models on the market and for me, the Comfortline was the one I chose. For the US Market, I recommend the Hydro Royal range of heat Pumps.

Lastly on specification, you do not need to match the air source heat pump to the make of spa pack you have. Balboa and Gecko would like you to do this of course, but you do not have to. I have a Balboa System and use a Comfortline Heat Pump.

Where should I locate the Air Source Heat Pump?

Each manufacturer will have different specifics for the mounting and location of the Air Source Heat Pump. However, let me give you a few general guidelines here.

You can’t mount them up against a wall. You must have air flow all the way around a unit. In general, you must have 1’ or 30cm around the entire heat pump.

Whichever direction the fan is blowing, should be around 1m or 3’ of clearance. What I mean here is you cant have these blowing directly onto a wall.

Lastly, you cant encase them in any way. They need to be outside, in the elements so they can do their job and extract heat from the air. Inside of a wooden box they are not going to be able to do that so do not box them in.

Where will I connect the pipes?

Connecting the pipes I have covered in my installation step by step article. You will need to be cutting into the pipe to the circulation pump, ideally just before or after the existing heater.

This is certainly something I can help with and if you send me a picture like the below showing the internal setup of your tub, I can advise accordingly.

Can I help you with your Air Source Heat Pump?

If I can help you with the supply of an Air Source Heat Pump, then please do get in touch. I have lots of models available in my online store that you can visit here. If you would like some advice about where to connect one, then please do let me know.

Happy Cheaper Hot Tubbin’

Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi


Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Today, I've helped over 1000 DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi

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