What is a Spa Heat Pump? (and how to choose the right one)

Whether you are installing a new spa pool or swim spa or upgrading the heating system on your existing spa, this article will explain everything you need to know about spa heat pumps and how to choose ...

Choosing the right heating and cooling solution is an important decision that can significantly affect the running costs of your spa.

Whether you are installing a new spa pool or swim spa or upgrading the heating system on your existing spa, this article will explain everything you need to know about spa heat pumps and how to choose the right one for your spa.

Most spas and swim spas come with a built-in electric heating element that will heat your spa, however, a heat pump can use 70% less energy than these electric elements - resulting in significant savings on power over time.

If you plan on using your spa regularly, a heat pump is an investment that will save you significantly on your spa running costs.


What is a Spa Heat Pump?


A heat pump is a stand-alone unit that sits outside near your spa pool and uses a compressor and a fan to extract heat from the air and transfer it to your spa water. 

A heat pump operates much more efficiently than a heater element - meaning you will use a lot less electricity to heat your water. You could use up to 70% less energy than an electric heater element and 55% less energy than a gas heater.

Depending on the outside air temperature, your heat pump will adjust it’s fan speed to allow it to heat the most efficiently.

A heat pump (like an air conditioner in your home) can also operate on a reverse cycle mode and cool the water in your spa - ideal for the warmer months of the year!


How a Spa Heat pump works

Without getting too technical, here’s a quick overview of the process a heat pump uses to transfer heat energy from the ambient air to your spa water!

  1. The liquid refrigerant inside the heat pump passes through an evaporator where it absorbs heat from the air and transforms into a gas
  2. An electric compressor then compresses the gaseous refrigerant
  3. As the gas is compressed, its temperature increases
  4. The warmed up gas moves into a condenser, where the heat is transferred to the water
  5. The refrigerant gas returns to a liquid state as it passes heat energy to the water
  6. The liquid flows through an expansion valve to release pressure and cool down
  7. The cycle repeats

Things to look for in a spa heat pump

Noise of operation

Check the sound level rating to ensure it’s not going to be too loud. (You may need to check with your local council regarding noise levels that are allowed in your neighbourhood). Sound levels are measured in decibels (dB /dB(A)). Anything with an ambient noise level under 55dB (A) is considered very quiet.


Heating Capacity 

Check the heating capacity level of the heat pump to ensure it’s sufficient for your spa or swim spa. Refer to the table below for our recommended sizes. Heating output is measured in kilowatts (kW).


Certified for use in Australia (AS/NZS 60335) 

Not all heat pumps have the correct electrical certification for use in Australia. Make sure you select one that has been certified to the correct standard to ensure you and your guests are kept safe.


Interfaces with your spa controller 

If you’re using a SpaNet® SV series controller in your spa or swim spa, you can interface a SpaNet® heat pump directly to your controller, meaning that it can be controlled directly from your spa’s control panel or even via the SpaNet® mobile App.

What size heat pump do I need for my spa? 

As a general rule, spas up to 2,500L in volume will need a heat pump of around 5.5kW to 6kW. 

A bigger spa or swim spa with a volume of up to 5,000L will need a heat pump with power output of 9kW.

The bigger the heating unit, the faster it will heat up. (But bigger heat pumps will use more power too!)


How much does it cost to replace a spa heat pump?

Heat pumps start at around $2,600 for a 5.5-6kW heat pump. Or around $3,100 for an 8kW heat pump.


How do you heat up a spa quickly? 

The only time you’ll need to heat your spa is when you are starting with cold water from empty.  Then after that, the set temperature will keep your spa consistent. (Remember, it is more efficient to maintain a water temperature rather than re-heat from cold each time).

Here are a few things to check to help your spa heat up quickly and efficiently.

Keep your cover on while heating to avoid heat loss.

Check the quality of your cover

A waterlogged cover, won’t insulate. Warm air can also escape around the hinge block or from the rim of your cover if it is not sealing in these areas. If your cover is absorbing water or worn, it’s time to consider replacing your cover.

Make sure your insulation is up to date 

Check if the insulation around your spa cabinet is present and in good condition. If you don’t have insulation, consider adding it

Can I run a heat pump in cold weather? 

Yes, you can as long as the ambient temperature does not drop below 10 degrees. If your temperature drops below this, the heat pump will switch off. In modern spas, when this happens, your controller automatically switches back to the electric heater to maintain the temperature in your spa.


Why does my heat pump keep tripping the circuit breaker? 

This is most likely caused by an insufficient water flow. If there is not enough water flow to your heat pump, airlocks can go in and the sensors think it is hotter than it should be. The thermal trip will switch your heat pump off to protect the hardware. To troubleshoot this, check and clean your filters, check the performance of your circulating pump - it can slowly give up the ghost, meaning it won’t be pumping enough water. 

Another alternative issue that can cause your heat pump to trip the circuit breaker is that it could be drawing too much power. Your electrician may need to install a larger capacity power circuit and larger circuit breaker.

How long does it take to heat a spa from cold? 

As a general rule, a spa pool will heat  0.5-1 degree per hour. Portable spas (up to 1,500L) will take from 18-24 hours to heat.


How long does it take to heat a swim spa?

A swim spa will take up to 72 hours to heat.

How do I keep my spa warm?

Some of the ways you can improve the efficiency of your spa heating include;

  • Making sure your spa cover is in good condition and sealing tightly
  • Checking the condition of your insulation in your spa cabinet (Or adding insulation if you don’t have any).
  • Setting a lower water temperature. Dialling down your set temperature by just 1 degree may not even be noticeable, but could make a big difference to your heating costs.


Should I leave my spa heater on?

Yes. Modern spas are designed to be left on to maintain the temperature. It uses less power to leave it on and maintain the temperature, rather than reheating from cold.

If you go away for an extended period of time, turn your spa down to 10 degrees and put it on away mode and it will only circulate water daily without using any energy for heating.

If your spa is connected the mobile app, you can login to the app the day before you come back and reset your desired temperature. (It will generally take 12-18hrs to heat up)


What is the ideal spa temperature for Australia? 

Keep your spa temperature between 32 - 34 degrees (Celcius) if you have children.
if you like hot water - you can set it up to 38 degrees for adult use (Celcius).

If you want to save money, setting your temperature lower will reduce your energy costs.


What temperature should I keep my spa when not in use?

If you’re going away for a week or more, you can set your spa temperature to 10 degrees and set your filtration system to just circulate once per day. 

If you only use the spa at the weekend, you can set your spa to ‘week mode’ which disables heating and filtration just runs for 1 hour per day, then from Friday to Sunday, it runs normally.


Can I run my spa on a solar heating system? 

Yes, all Spa World spas can be run off solar power, however solar only works when the sun is out. What we find is that the spa ends up getting really hot in summer and not hot enough in winter, which is opposite to the way you probably want to use it!


Can a spa heater heat a pool?

No. Because the chlorine requirements and heating requirements are different in a pool, they are not designed to be interchangeable. We recommend a specific pool heater.


What is the most energy-efficient spa heater? 

Inverter heat pumps are up to 6 times more efficient than an electric heater element. 

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