What size heat pump for my pool?

Pool heat pumps work by capturing heat from the air and transferring it into your pool water. This makes them an energy-efficient solution for maintaining the perfect swimming temperature – but only if you choose the right capacity. The right-sized pool heat pump not only helps your pool stay warm and inviting but also keeps energy costs in check. It’s about finding the perfect balance to suit your swimming pool’s volume and the environmental conditions you’ll be using it in. Wondering ‘what size heat pump for my pool’?  We’ve got you covered. NCS Pool Heating Systems has been supplying and installing heat pumps in NSW pools for over 30 years. In this article, we break down how to calculate the correct pool heat pump size so that you can swim comfortably while saving money in the long term.

What is a pool heat pump?

A pool heat pump is an energy-efficient device that transfers heat from the air to your pool water, keeping it warm and comfortable.  Unlike traditional gas or electric heaters, heat pumps rely on atmospheric warmth to maintain your pool’s temperature, helping to extend your swimming season while lowering energy costs and reducing carbon emissions. There are two main kinds of pool heat pumps:

• On/off heat pumps: These operate by switching on until the desired temperature is reached, then shutting off. They turn back on when the water cools but can be less efficient over time.
• Inverter heat pumps: These are equipped with advanced technology that adjusts the fan and compressor speed to maintain the set temperature efficiently. A full inverter heat pump can self-regulate, using less electricity compared to on/off models.

Inverter heat pumps are also rated by their Coefficient of Performance (COP), which measures how much heat is produced relative to the energy consumed.  A heat pump with a COP of 6 delivers six units of heat for every unit of electricity used, making it significantly more efficient.  The higher the COP, the better the performance and cost savings. For instance, Rheem inverter pool heat pumps are designed with high-efficiency compressors and variable-speed fans, offering an impressive COP rating to deliver maximum heat output with minimal energy use.” Learn more about how pool heat pumps work.

Factors to consider when choosing the right size pool heat pump

Are you using a pool cover?

If you have a pool, you need a pool cover – especially in Australia. A pool cover (pool blanket) reduces evaporation and retains the temperature of the water, allowing you to take advantage of a smaller pump.  Although perfect for fun in the sun, our climate can cause an uncovered domestic pool to lose up to 55,000 litres annually through evaporation. When water evaporates, so too do expensive pool chemicals and salts, losses which are costly, but thankfully easily avoided. Choosing a properly fitted solar pool cover can prevent up to 97% of evaporation and hundreds of dollars worth of pool care products depending on the size of your pool. For a free measure and quote using Nearmap Technology, click here.

Pool location and swim season

Where you live is just as essential as the size of your pool. The cooler the climate, the higher the kW output required. If you live in a warm environment, your pool heat pump won’t need to work as hard. A small to mid-sized pool heat pump would be perfect for a medium-sized swimming pool. If you want to swim in your pool year-round, you may need a larger pool heat pump. You will also need to determine the average temperature of your pool’s environment throughout the coldest month you’ll be using it.  Make sure to consider other factors like humidity, wind chill, and nighttime temperatures. If you live in a dry environment with strong wind and low night temperatures, investing in a bigger pool heat pump would be wise. Designed for Australian conditions, the Rheem Thermal Compact Inverter Series operates with an outside temperature of -5°C to +43°C and are available in a range of sizes to suit the volume of your swimming pool.

Water temperature set

The extent to which you want the water temperature to increase is an important factor to consider. Basically, the greater the rise, the larger the pool pump required, as it will increase the water temperature quicker per unit time than a smaller one.

Filtration working time

Determine how and how often you will use your pool. You have a choice of two heating methods: warming from a chilly state or maintaining a fixed temperature.  If you are swimming regularly, you may want to maintain the heating at all times rather than heating from cold.

How to calculate pool size

It’s usually easier and more reliable to have a professional technician size your heat pump. Experts have the knowledge and resources to ensure every factor is accounted for, avoiding costly mistakes and maximising heating efficiency. Still, it’s worth knowing how the recommendation is made. Here’s a general guide to sizing your heat pump based on your pool’s dimensions.

Step 1. Calculate your pool’s volume

Knowing your pool’s water volume is essential for selecting the right heat pump. Larger pools hold more water and need a heat pump with greater capacity to efficiently maintain a comfortable temperature. Don’t know your pool’s volume? No worries—it’s easy to figure out. Measure the length and width of your pool to find the surface area. Then, multiply that by the average depth to calculate the volume. For instance, if you have a backyard pool measuring 8m long, 4m wide, and an average depth of 1.5m, the surface area would be 32m² (8 x 4). Multiply that by the depth, and you get a volume of 48 cubic metres (32 x 1.5). Since 1 cubic metre equals 1,000 litres, your pool holds 48,000 litres.

Step 2. Confirm the required kW

With your pool volume calculated, the next step is to determine the power needed for your heat pump to effectively heat your pool. A quick rule of thumb is to divide your pool’s volume (in litres) by 2,500.  For example, if your pool holds 48,000L, the calculation would be 48,000 ÷ 2,500 = 19 kW (note, this number assumes a pool cover will be used).  This rough estimate will set you in the right direction. From there, you can explore your options and get tailored support to confirm your exact requirements.

Step 3: Account for other factors

When choosing a pool heat pump, a simple rule applies: smaller pools need smaller pumps, while larger pools require more power.  If you’re unsure, it’s better to opt for a slightly larger unit rather than a smaller one. While the upfront cost may be higher, the long-term savings on energy bills will make it worthwhile. But as mentioned above, several other factors can influence your heat pump’s efficiency:

• Climate: The efficiency of a pool heat pump varies with ambient temperature and humidity. Cooler climates may need a larger pump to maintain consistent heating.
• Pool cover: Without a pool cover, your heat pump will need to work harder to maintain warmth. Using a cover can cut heating costs by up to 80%, making it an essential investment.
• Pool type: Above-ground pools or exceptionally large pools require more energy to maintain a steady temperature, potentially increasing costs.

By taking these factors into account, you can find the proper size heat pump for your pool. If the exact heat pump capacity isn’t available, opt for the closest match and round up rather than down. It’s always better to have a little extra power than not enough!

Can pool heat pump sizing impact energy efficiency?

Absolutely! Choosing the right size pool heat pump is key to maximising energy efficiency.  An undersized pump will struggle to heat your pool, working overtime and spiking your energy costs.  On the other hand, an oversized pump may cycle on and off too frequently, wasting energy and wearing down the system.  By selecting a heat pump tailored to your pool’s size and needs, you’ll enjoy consistent water temperatures, lower energy bills, and a pump that performs optimally without unnecessary strain.  

Get the right size pool heat pump with NCS

A well-sized heat pump is the key to enjoying a pleasant water temperature all year round without breaking the bank. It ensures energy efficiency, lower running costs, and a longer-lasting system.  Go too big, and you might overspend unnecessarily; too small, and you risk overworking the unit and inflating your energy bills. Choosing the right heat pump can feel overwhelming, but the team at NCS Pool Heating & Filtration Systems makes it simple. As the exclusive authorised distributor of Rheem Heat Pumps in Newcastle, Central Coast, The Hunter and Mid North Coast, we are experts in their sizing. We’ll assess your pool’s unique needs and recommend the ideal inverter heat pump to keep your water warm and your costs low.  Get in touch today and let us help you create a comfortable swimming experience.