What are Air-to-Water Heat Pump Pool Heating Technologies?
Air-to-water heat pump pool and spa heating technology utilizes ambient air to heat pool and spa water efficiently, significantly reducing energy consumption compared to traditional gas or propane fired heating methods. By extracting heat from the surrounding air and transferring
it to the pool and spa water through a compressor, condenser, evaporator, and expansion valve system, these units offer both environmental and performance benefits. Pool and spa heat pump water heaters (HPWHs) produce fewer greenhouse gas emissions and have lower
operating costs, making them environmentally friendly and cost-effective options for maintaining comfortable swimming temperatures. With proper installation and maintenance, air-to-water heat pump pool and spa heating technology can provide reliable and consistent heating performance, ensuring enjoyable swimming experiences while minimizing the ecological footprint associated with pool and spa temperature maintenance.
Distinguished by their scroll compressors and titanium heat exchangers, higher-efficiency heat pump pool and spa heaters optimize performance and durability.
Unlike conventional reciprocating compressors, scroll compressors utilize two rotating coils to compress refrigerant gas, offering enhanced reliability and energy efficiency. This innovation signifies a significant stride towards sustainable and economical heating solutions, poised to redefine the pool and spa heating landscape.
In addition, titanium heat exchangers offer numerous advantages over other materials like copper or stainless steel. They boast exceptional corrosion resistance, ensuring longevity and reliability even in harsh pool water environments with high chlorine or salt content. Their durability allows them to withstand high temperatures and pressures without deformation or degradation, resulting in a longer lifespan and reduced maintenance requirements. Titanium’s excellent thermal conductivity ensures efficient heat transfer, leading to optimal heating performance and energy savings. Additionally, titanium is compatible with various water chemistries and environmentally friendly, making it a safe and sustainable choice for pool heating systems. Overall, titanium heat exchangers deliver superior performance, durability, and environmental benefits, making them the preferred option for pool and spa owners seeking efficient and long-lasting heating solutions.
When to Consider This Measure?
Heat pump pool and spa water heaters run most efficiently in locations that remain above 45°-50°F year-round.1 Indicating warmer climates are best for implementing heat pump pool heating technology. Since air-to-water heat pump technology requires heat from the surrounding air to heat water, the cooler the outside air they draw in, the less efficient they are, potentially resulting in higher energy bills. With outdoor pools typically in use during warm
and mild weather, and considering California’s mild to warm climate, energy use is a minimal issue. In addition, it is necessary to provide adequate space and clearance around the heat pump pool and spa heater for proper airflow and service.
1 Source: U.S. Department of Energy, Heat Pump Water Heaters
Sizing a Heat Pump Pool Heater
Sizing a HPWH for pool heating requires considering various important factors. The most critical are pool surface area and temperature differentials. Environmental variables like humidity and average wind speed which play a part since HPWHs utilize surrounding air for heating. A trained pool professional can perform a sizing analysis to determine the proper
pool and spa HPWH size.
Pool water temperatures usually vary between 78°F to 82°F, with 78°F being recommended by the American Red Cross for competitive swimming and optimal fuel savings. However, young children and the elderly may prefer 80°F or higher for more comfortable swimming. Increasing the temperature by a single degree can result in 10%–30% higher energy costs, highlighting the importance of an efficient pool heating system to manage costs effectively. 2
Heat pump pool and spa heaters are rated by Btu output and horsepower (hp). Some standard sizes include 3.5 hp/75,000 Btu, 5 hp/100,000 Btu, and 6 hp/125,000 Btu.
Energy.gov provides a method to calculate an approximate heat pump heater size for an outdoor swimming pool. 3 Their method uses the design temperature rise (difference between desired pool temperature set point and average temperature for the coldest month) and the pool area to find the pool’s required BTU/h heating load. This calculation can give you an estimate of the scale of heat pump needed to heat your pool.
2 Source: U.S. Department of Energy, Managing Swimming Pool Temperature for Energy
Efficiency
3 Source: U.S. Department of Energy, Heat Pump Swimming Pool Heaters
System Configurations
Below is an example of a general plumbing layout for heat pumps used in pools and spas. Besides the heat pump, these systems typically include a skimmer, filter, pool pump, water inlet and outlet connections, main drain, chemical feeder, check valves, and isolation valves. Reputable manufacturers of heat pumps include AquaCal, Hayward, and FibroPool. For the most accurate piping configuration tailored to your specific heat pump model, refer to the manufacturer’s literature provided with your unit. 4
- Heat Pump: The central device responsible for heating the pool or spa water. (4)
- Filter: Ensures that the water entering the heat pump is clean and free of debris. (3)
- Pool Pump: Circulates water through the pool, ensuring it passes through the filtration system for cleaning. (2)
- Water Inlet and Outlet Connections: Pipes that allow water to flow into and out of the heat pump.
- Check Valve: Prevents water from flowing back into the heat pump, protecting it from damage. (6)
- Isolation Valves: Allow for the isolation of the heat pump from the rest of the plumbing system for maintenance. (5)
- Skimmer: A device that removes debris from the surface of a swimming pool, either manually with a net or automatically as part of the pool’s filtration system.
- Main Drain: Located at the bottom of the pool, it is used to lower the water level or to circulate water from the bottom of the pool.
- Chemical Feeder: Automatically dispenses sanitizing chemicals, such as chlorine or bromine, into a swimming pool to maintain water cleanliness and safety. (7)
- Suction Lines: Pipes that carry water from the skimmer or main drain to the pump. (1)
- Return Lines: Pipes that return the filtered and heated water back to the pool or spa. (8)
4 Disclaimer: The California Energy Design Assistance (CEDA) program is not sponsored by any heat pump manufacturers. If a heat pump manufacturer does not see their name listed on this page and would like it mentioned, please contact CEDA to provide information about your product at ceda@willdan.com.
What Are the Benefits?
- More energy-efficient than traditional heating methods, since air-to-water heat pumps don’t have to generate heat which allows for lower energy costs
- Environmentally smart choice by utilizing heat from the air, cutting down on greenhouse gas emissions, and supporting decarbonization efforts like CARB 2030 goals
- Provides consistent and reliable heating for pools and spas year-round by maintaining desired temperatures in moderate weather conditions
- With proper maintenance, heat pump pool heaters typically last longer than gas-fired pool heaters
- Some heat pump pool heaters can function for both heating and cooling purposes, enhancing functionality and versatility
- Improved safety since pool heat pumps do not involve on-site combustion or open flames, which eliminates the risk of gas leaks or carbon monoxide poisoning
Additional Benefits
- Integration with solar water heaters 5: Heat pump pool heaters and solar water heaters can serve different purposes, but they can complement each other. Having both systems installed together can assist in efficiency of the heating systems and supplement energy costs. However, a solar water heater has a much smaller impact, whereas a HPWH can greatly impact your pools heating on a larger scale and provide more benefit.
- Integration with thermal storage systems: Thermal energy storage (TES) captures and retains excess heat or cold, crucial during high-demand periods on the grid. It optimizes energy usage by releasing stored energy when needed most. Integrating heat pumps and TES, especially with solar technology, offers substantial advantages. Solar collectors gather and store excess heat, easing the load on solar and air-based heating systems, prolonging their lifespan, and reducing the need for additional power generation. While integrating TES with air-to-water HPWH poses initial installation complexities and maintenance challenges, their synergy promises substantial efficiency gains when operational.
5 Source: U.S. Department of Energy, Solar Water Heaters
What Are the Challenges/Constraints?
- Higher initial installation costs compared to gas-powered pool heaters
- May have a diminished performance in colder climates due to the lower air temperatures
- Longer initial heating times compared to traditional water heaters, although they maintain consistent temperatures once warmed
- Requires clean air for optimal operation, potentially increasing maintenance needs in areas with poor air quality
- Systems can be relatively large and typically require adequate space for installation
- May require dedicated electrical circuits or higher voltage supplies
- While current pool and spa heat pumps are designed for quiet operation, some models may produce noticeable noise levels during operation
Additional Considerations
One significant way that pools lose efficiency is in water evaporation. The evaporation rate for outdoor pools depends on various environmental factors including air quality, temperature, and wind speeds. Covering pools when not in use reduces evaporation, helps conserve water and saves energy. However, opaque covers may reduce the effectiveness of air-to-water HPWH. Opt for covers that allow sunlight penetration to optimize efficiency while still protecting the pool from evaporation. In addition, the current CA Energy Code requires pool covers for outdoor pools and spas that are served by heat pump pool heaters in accordance with Section 110.4(b)2. 6
Air-to-water HPWH systems are renowned for their high efficiency, typically measured by the coefficient of performance (COP). With COP values ranging from 3 to 7, these systems can generate up to seven times the energy they consume, making them an incredibly efficient choice for heating pool and spa water.
Who is Eligible for Inducements?
Air-to-water pool and spa HPWHs are eligible for inducement as an electrification measure if the pool or spa uses HPWHs as the primary source for water heating.
For a project to be eligible for inducements, they must:
- Install a heat pump pool or spa heating system serving a commercial, public, or high-rise multifamily building
- Submit engineered, stamped, and permitted construction plans demonstrating that the heat pump pool or spa heating system design fully complies with all state and local jurisdiction requirements and regulations
- Provide equipment submittals stamped and approved by the responsible engineer of record
- Submit equipment-cost information
- Participate in on-site verification and possible data logging of the system
Note:
- Project may be selected by PG&E for a future case study
- Measure requirements are subject to change; this guide reflects information available as of April 2025 — for the most current measure requirements, contact CEDA@willdan.com
