Founder | BPI® Energy Auditor Certified Professional
Swimming pool heat pumps provide an excellent way to heat your pool. However, not all heat pumps are created equal–some are more energy efficient than others. How much can you save if you switch to a variable-speed heat pump?
Variable-speed pool heat pumps save between 70 and 90 percent daily on heating energy, depending on the pool’s capacity and climate. For example, a 74% reduction in heating energy for a 25,000-gallon pool in the U.S. would save $1.28 daily, shaving $468 off an annual bill.
In this article, I’ll help you calculate savings using a variable-speed pool heat pump. I’ll also discuss how these pumps work and the factors affecting your savings.
Let’s get started!
What Are Variable Speed Pool Heat Pumps?
A variable-speed pool heat pump is a pump that runs at varying speeds to match the pool’s heating needs.
This means the pump only runs at full capacity sometimes, resulting in less energy usage and lower electricity bills.
The idea behind the variable speed is that swimming pools have different heating needs at various times and seasons.
For instance, due to frequent use, your pool may require more heating in the summer than in winter.
Unlike traditional single-speed pumps, which have a standard speed of 3,450 revolutions per minute (RPM), a variable-speed pool heat pump allows you to adjust the settings to match your pool’s heating needs.
This results in greater efficiency and lower energy consumption, leading to significant savings on your electricity bills.
If you want to install a swimming pool, check out this article for insulating concrete form (ICF) pool construction guide.
How Much Do Variable Speed Pool Heat Pumps Save?
Before diving into the nitty gritty of how much you’ll save by using a variable-speed pool heat pump, let’s understand how this pump helps save energy and electricity bills.
Both single and variable-speed pool heat pumps have speeds measured in revolutions per minute. However, with a variable-speed pool heat pump, you can operate at lower rates for a run cycle.
According to The Pump Affinity Law, a pump’s motor speed and flow rate are directly proportional to energy consumption.
Based on this law, the higher the pump’s motor speed in RPMs and flow rate, the higher its energy consumption.
Conversely, the lower the pump speed and flow rate, the less energy it consumes.
That’s why variable speed pumps are so efficient–they can adjust their speed to match your pool’s heating needs, resulting in significant savings on electricity bills.
In short, using a variable-speed pool heat pump = fewer RPMs = less energy consumption = low utility bills.
Consequently, you’ll have more money in your pocket.
Here is a table to help you conceptualize The Pump Affinity Law in the working of your variable speed pool heat pump:
| Pump Speed (RPM) | Flow (GPM) | Power (Watts) |
| 3,450 | 66 | 2,000 |
| 3,000 | 55 | 1,157 |
| 2,400 | 44 | 593 |
| 1,800 | 33 | 250 |
| 1,200 | 22 | 74 |
| 600 | 11 | 9 |
Table 1: Pump affinity law values
Now that you have the context of how variable-speed pool heat pumps aid in energy conservation, let’s dive into the real deal–calculating the savings.
We’ll use a 25,000-gallon swimming pool for this demonstration.
Most 25,000-gallon residential swimming pools have a turnover rate of 24 hours.
The first question to ask ourselves is, how many hours will a single-speed pool heat pump running at 3,450rpms consuming 2,000 watts and a flow rate of 66 GPM take to turn over this pool?
={(25,000 gallons ÷ 66 GPM) ÷ 60 minutes)} = 6.3 hours
Using the above rate, let’s calculate the watt-hours this single-speed pool heat pump will consume daily to turn over the pool:
(6.3 hours ✕ 2,000 watts) = 12,600 watt-hours or 12.6kWh.
Now, let’s apply The Pump Affinity Law to determine how much a variable-speed pool heat pump will use.
The pump is set at a lower flow rate of 33 GPM, drawing 250 watts (based on the table). How long will this variable-speed pool heat pump take to turn over the 25,000-gallon pool?
{(25,000 gallons ÷ 33 GPM) ÷ 60 minutes)} = 13 hours.
Using the above rate, let’s calculate the watt-hours this variable-speed pool heat pump will consume daily to turn over the pool:
(13 hours ✕ 250 watts) = 3,250 watt-hours or 3.25kWh.
So, how much energy does this variable-speed pool heat pump save?
The savings on energy = (12.6kWh−3.25kWh) = 9.35kWh per day or 3,412.75kWh annually.
In terms of percentage, the energy saving will be:
{(9.35 ÷ 12.6) ✕ 100)} = 74 percent
Based on the above energy savings, how much money will you save?
According to the U.S. Energy Information Administration, the average retail electricity price in the U.S. is 13.72 cents per kilowatt-hour. Therefore, let’s calculate the amount you’ll save using this price:
Savings = (13.72 ✕ 9.35)= $128.28 per day. If you’re a U.S. resident, you’ll save $468 on your annual heating bills by using a variable-speed pool heat pump.
Important points to note:
● You should substitute values in the above calculation for your case. For instance, instead of using a 25,000-gallon pool, replace it with your pool’s capacity.
● You should check your variable-speed pool heat pump for its flow rate in gallons per minute. After getting this rate, refer to The Pump Affinity Law table above for its equivalent wattage and use it in your calculations.
● The more you reduce your pump’s motor speed, the more your potential savings on energy. So, you can set up your variable-speed pool heat pump at its lowest RPM before running any calculations.
Factors That Affect Savings
You may notice that your savings are higher or lower than another person using a variable-speed pool heat pump. The variation results from the following factors.
Your Pool’s Size
Swimming pools come in different sizes to meet different needs.
In most cases, the number of people using a swimming pool determines its size–the higher the number, the larger the swimming pool.
The swimming pool’s size determines its capacity. The larger the pool, the higher the capacity in gallons and vice versa.
A pool’s capacity determines the heating energy needed and the turnover rate.
High-capacity pools will need high flow rates in gallons per minute, translating to more energy use and fewer savings.
Here’s a table to help you see how pool size affects the flow rate, the required pump’s revolution, and energy cost per hour:
| Dimensions | Capacity (gallons) | Flow Rate (GPM) | Revolutions (RPM) | Cost Per Hour |
| 15 ft x 30 ft | 16,000 | 25 | 1,600 | 2.6 cents |
| 18 ft x 36 ft | 24,000 | 35 | 1,800 | 3.65 cents |
| 20 ft x 40 ft | 30,000 | 42 | 2,000 | 5.0 cents |
| 22 ft x 46 ft | 36,000 | 50 | 2,400 | 8.3 cents |
Table 2: The effect of pool size on the VS pool heat pump’s operation
Frequency of Use
How often you use your swimming pool is another factor that affects the total savings you make with a variable-speed pool heat pump.
The more often you use it, the higher the energy consumption and thus more electricity bills. The opposite is also true.
Your Climate
If you live in a warmer climate, the pump will use more energy to heat the pool due to its frequent use.
On the other hand, the pump will use less energy to heat a swimming pool in colder climates due to its limited use.
Therefore, if you live in a warmer area, you should expect to save less than someone in colder weather.
Flow Requirements of Other Water Features
Suppose you have other water features like waterfalls, cleaning systems, and raised spas in your pool. In that case, their flow requirements will also affect the savings.
The higher the flow rate needed, the higher the electricity bills, and vice-versa.
Fortunately, with a variable-speed pool heat pump, you can adjust your speed settings to match all your swimming pool’s needs without investing in multiple pumps.
The Working of Variable-Speed Pool Heat Pumps
Variable-speed pool heat pumps have a magnetic motor you can precisely control to regulate speed. The motor can run at low, medium, and high speeds.
The pump circulates the water in your pool at a low speed without using much energy. This is because moving a small volume of water takes less energy at low speeds than a higher volume.
On the contrary, the motor uses more energy at higher speed settings but moves more gallons per minute.
Variable-speed pool heat pumps work based on the heat transfer principle.
As the water circulates through the pool pump, it goes through the pump’s heater and a filter. The heater’s fan draws in the outside air and passes it over the heat exchanger.
The liquid refrigerant in the heat exchanger then absorbs the outside air’s temperature. Next, it passes through a compressor to increase its heat.
The very hot refrigerant then goes through the condenser coil, releasing its heat into the pool water.
The refrigerant then goes back to the compressor, and the cycle repeats itself until the pool reaches your desired temperature.
A point worth noting is that heat pump pool heaters are efficient within an outside temperature range of 45°F and 50°F (7.22°C and 10°C).
If the outside temperature gets cooler than this range, the heat pump draws in cooler air, reducing its efficiency.
However, this is a minor issue since most people use pools during the warm and mild seasons.
Advantages of Variable-Speed Pool Heat Pumps
Before shopping for a variable-speed pool heat pump, you should know its benefits and how it will enhance the quality of your life.
Luckily, this pump has the following features and benefits.
Energy Efficiency
As already discussed, variable-speed pool heat pumps are energy efficient. They can save up to 90 percent on a pool’s heating energy.
Saving energy is not only good for the environment but also your wallet. You don’t have to break the bank when you can leverage the advantages of a variable-speed pool heat pump.
Quiet Operation
The magnetic motor used in variable-speed pool heat pumps runs at lower speeds. The lower speed helps keep noise levels down, allowing you to enjoy a peaceful and quiet swimming experience.
Even when running at tops speeds, the magnetic motors make less noise than their standard counterparts used in conventional single and double-speed pool heat pumps.
Longer Heating Life
Due to the slow speeds, variable-speed pool heat pumps have a longer heating life.
The motor runs at slower revolutions, reducing wear and tear on its parts. Minimal wear and tear translate to an increased lifespan.
The longer lifespan means you will spend less on frequent repairs and replacements.
Excellent Water Filtration
When the flow rate is low, the filters have sufficient time to trap and retain debris. Since variable-speed pool heat pumps operate at low speeds, they are excellent at water filtration.
Standard pool heat pumps that run at 3,450rpm have higher chances of experiencing bypasses than variable-speed pool heat pumps.
Final Thoughts
Variable-speed pool heat pumps are your go-to option to save energy. These heaters have variable speeds, which makes it possible to reduce energy consumption.
Moreover, these pumps are quieter, guarantee a longer life, and have improved water filtration capabilities than single-speed pool heat pumps.
Now that you know how much variable-speed pool heat pumps save, check out this article for 14 great efficient options for pool heating.