Swim season is woefully short. With a pool heater, you can enjoy several more months of swimming every year. When it comes to heaters, you have four choices – an electric resistance heater, a gas heater, a heat pump and a solar heater.
If energy efficiency, safety and durability are your main must-haves, a heat pump will fit all your requirements. You can even use a heat pump in conjunction with an existing gas heater to reduce the overall operating cost and further extend the pool season.
Pool heat pumps work similarly as HVAC heat pumps. As water flows into the heat pump, the pump’s fan uses heat from the ambient air and sends it to the evaporator coil. The refrigerant in this coil absorbs the heat and transforms into gas, which gets heated more by the compressor.
The condenser uses the gas’ heat to warm the water before the water flows back into the pool. At that point, the condenser cools the gas until it returns to its liquid refrigerant form, sending it back to the heat pump’s evaporator. The entire process is extremely energy-efficient.
Each heat pump on our list was chosen with efficiency and longevity in mind. However, not every heat pump on the list will be appropriately sized for your swimming pool. To figure out what size heat pump you need, check out the information in our buyer’s guide.
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Best Pool Heat Pumps
Pool Heat Pump Buying Guide
There are multiple factors at play when sizing a heat pump for your swimming pool. In this guide, we offer the general parameters you should follow to determine the number of BTUs that are appropriate for your pool. The heat pump’s flow rate is important too, and it must correspond with the pipes’ maximum flow rate.
For residential in-ground and above-ground swimming pools, there are no hard-and-fast efficiency rules. Of course, we assume that you want to save money. Therefore, this guide explains how a heat pump’s energy efficiency is calculated. We also cover features that you should look for in terms of durability.
BTUs
Heat pumps may be cost-efficient to run, but they don’t heat the water instantly. If you undersize the heat pump’s BTUs, the water may take days to heat to your desired temperature. In some cases, it may not be able to reach that temperature at all. Therefore, correctly sizing a heat pump is crucial to achieving optimal efficiency.
A few simple math equations can help you determine the number of BTUs you need a heat pump to push out. Multiply the pool’s surface area by the temperature rise (the difference between the lowest average ambient temperature to the desired pool water temperature). Then, multiply that answer by 12.
For a swimming pool with a surface area of 450 square feet and a temperature rise of 15 degrees, the minimum BTUs needed is 81,000. Pools in windy areas or regions with low humidity may require a 10-percent bump in BTUs while pools without a cover may need up to 50,000 extra BTUs.
Flow Rate
The flow rate measures the proficiency of a heat pump’s ability to circulate water. Like the BTUs, the flow rate is another spec that must be properly matched. Otherwise, you risk overheating the heat pump. Instead of sizing the flow rate to the swimming pool’s surface area, you must size it according to the pool’s pipes.
Every heat pump has a minimum and a maximum flow rate, which is described in gallons per minute (GPM). The water flowing through the pipes should fall within that range. A simple meter can measure the pipes’ exact flow rate, which is determined by the pipes’ diameter and length. The wider the diameter, the higher the rate.
Clogs and obstructions will impede the water flow, but there are several steps you can take to prevent this problem. Regularly clean the filter and pump basket, and always maintain the water’s chemistry. Also, make sure the heat pump’s water pressure switch is inspected annually. Finally, keep all the valves completely open.
Energy Efficiency
While you’re looking at the details of the heat pumps we’ve reviewed, you’ll see the acronym COP, (coefficient of performance). The COP ratio measures the energy generated by the heat pump compared to the energy it uses. For instance, a 4.4 COP means the heat pump produces 4.4 kW for every 1 kW it consumes.
The COP of a pool heat pump ranges from about 2.0 to 7.0. Heat pumps with high COP and BTU ratings cost the least to run. When comparing the COP of different models, keep in mind that the testing temperatures vary among manufacturers. Most stick with an 80 degree Fahrenheit ambient and water temperature.
Heat Exchanger
One major internal component found in a pool heat pump is the heat exchanger. The heat exchanger’s purpose is to take the heat out of the refrigerant and infuse it into the pool water. When it comes to the heat exchanger, durability is key.
In the past, copper and cupronickel (a copper and nickel alloy) were manufacturers’ materials of choice due to their cheap production costs. Now, titanium has come into favor as this material stands up better to rust and corrosion. A heat exchanger made of titanium is the best choice for saltwater swimming pools.
Compressor
A heat pump comes equipped with one of two varieties of compressors – a reciprocating compressor or a scroll compressor. The reciprocating type contains pistons that pull the refrigerant in its gas state into a chamber during the downstroke. On the upstroke, the pistons compress the gas, causing it to get hot.
Scroll compressors make the most of the energy they produce because compression occurs nonstop. This type of compressor has one stationary scroll and one orbital scroll. As the orbital scroll revolves around the stationary scroll, the gaseous refrigerant is compressed and heated.
Normally, reciprocating compressors are used in low BTU models. In comparison to scroll compressors, reciprocating compressors are less efficient as a lot of energy is lost due to the lack of compression during the downward strokes. Since scroll compressors have fewer moving parts, they last longer and operate quieter.
Installation Requirements
Pool heat pump installation is usually handled by a professional technician unless you have installation know-how. If you do hire a technician, make sure he installs the heat pump on a sturdy concrete slab to reduce the pump’s vibrations.
The heat pump should be put outdoors at least 2 feet away from any wall to ensure proper airflow. Also, it will need its circuit breaker to handle the startup current. Depending on the BTUs of the pool heat pump, the amperage must range from 30 to 70.
When setting up the heat pump’s location, ensure that it’s the last component in the circulation line. However, if the pool has a chlorinator, the heat pump should be plumbed in before the chlorinator to prevent heat exchanger corrosion.
FAQs
Can I Use A Heat Pump With My Existing Gas Heater?
Absolutely. In fact, a dual gas-heat pump configuration will give you more time each year to enjoy your swimming pool. Additionally, you’ll slash the operating cost by half, and drastically reduce your swimming pool’s carbon footprint.
To make the heat pump the main heater and the gas heater the supplemental heater by routing the pipes to send water to the heat pump first. Then, adjust the thermostat on the gas heater to a lower temperature than the heat pump, so it the gas unit will act as an auxiliary heater.
Do I Need to Winterize My Heat Pump?
Pool heat pumps can last as many as 20 years, especially those with an automatic defrost function. However, it’s still wise to winterize your heat pump. To do so, drain the water and protect the unit with a moisture-resistant cover. If you install a bypass between the return and flow lines, it will be easier to drain the water.
How Do Heat Pumps Compare to Other Kinds of Pool Heaters?
Heat pumps have the advantage over gas heaters as they consume approximately 75 percent less energy. Heat pumps are also safer because they don’t have a pilot light or release harmful carbon dioxide into the air. On the other hand, gas heaters warm the water faster, and they operate at a lower ambient temperature.
In comparison to electric resistance heaters, heat pumps are more cost-efficient. Since they require less electricity to run, heat pumps cost up to five times less to operate. However, as with gas heaters, electric resistance units still work at a lower temperature than heat pumps.
Out of all four types of pool heaters, solar heaters cost the least to run daily. Regardless, heat pumps offer several benefits that solar heaters don’t. Heat pumps function on overcast days, and they take up less space than solar panels. Plus, heat pumps can maintain a set temperature without purchasing a separate controller.
Pool Heat Pumps: Recap
Models with a titanium heat exchanger and scroll compressor are the most durable. With proper care and winterizing, you can get at least 10, if not 20, years of reliable performance out of a pool heat pump, making them an excellent investment in your swimming pool.
Although heat pumps are slower to warm the water, they are the most energy-efficient and reliable type of pool heater. They’re also easy to size. All you need to know are the surface area of your swimming pool, the temperature rise and the pipe diameter to get solid ballpark BTU and flow rate figures.