Air To Water Heat Pump:Most Economical Heating Solution!

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By Debarghya Roy


Air-to-water heat pumps are a cutting-edge and increasingly popular way for homeowners and commercial customers to maximize energy savings, reduce environmental impact, and enjoy improved comfort.

Air To Water Heat Pump

An air-to-water heat pump uses outside air as a renewable energy source to transfer heat into a home or commercial space. Use of advanced technology; these systems draw in external air, extract the available thermal energy, and convert that thermal energy into usable hot water or heating/cooling capacities, enabling you to maintain optimal temperatures throughout your indoor spaces with minimal effort and expense.

Overview Of Air To Water Heat Pumps

Air-to-water heat pumps are an efficient and cost-effective way of providing heating, hot water, and cooling in residential and commercial settings. They work by transferring heat from the outside air into a liquid which can be circulated through a building’s heating system to provide warmth. 

With an operating temperature range of 10 – 40 degrees Celsius, these systems can provide consistent comfort in any environment without needing additional fuel or energy sources. By utilizing electricity, air-source heat pumps absorb ambient warmth and release low-carbon emissions that make them ideal for eco-friendly homes or businesses. 

Additionally, they operate quietly while saving energy and money on utility bills with their high-efficiency ratings of up to 400%. Air-to-water heat pumps offer substantial benefits over traditional HVAC systems. They are becoming increasingly popular worldwide, so let’s discuss what makes them a viable option. Discover how to use this advanced technology at your home or business today.

Definition And Key Features

An air-to-water heat pump is an efficient heating system that uses the refrigeration cycle to extract heat from the outside air and transfers it into hot water.

While traditional heating systems consume large amounts of electricity, an air-to-water heat pump relies on a refrigerant to cycle between its two states: evaporating and condensing. It provides valuable thermal energy with as little as one-third or even one-fifth of the electricity used in conventional electric boilers.

Air source heat pumps are typically composed of four main parts – 

  • Compressor,
  • Condenser, 
  • expansion valve and 
  • evaporator coil 

All these help convert low-grade Fahrenheit temperature outdoors into hot water suitable for residential use inside your home.

This technology requires minimal maintenance, although some units allow external cleaning agents such as quaternary ammonium compounds (QACs), which help break down bacteria and other organic matter on contact surfaces.

Air-source heat pumps come in various shapes and sizes, including split systems, full-house warm air furnaces, storage tank types for domestic hot water only, and hybrid models available at retail stores across the US.

Understanding The Technology

Air-to-water heat pumps provide an extremely efficient and cost-effective way of harnessing energy from the air and transferring it indoors. They work by drawing in outside air, which is then processed through a refrigerant system before releasing it into the home environment at higher temperatures.

This process is similar to that used for regular refrigerators or air conditioners but on a larger scale. The critical components are a compressor, heat exchanger, expansion valve, and circulating refrigerant.

The compressor transfers thermal energy from incoming warm air to cool liquid refrigerant during the compression process. Next, this heated liquid passes through a heat exchanger, where its temperature increases significantly as energy is released via thermal exchanges with aluminum alloy fins connected to different parts of the tubing coil inside the equipment’s interior parts.

This heated liquid then enters an expansion valve that reduces its pressure – bringing down its boiling point so that further cooling occurs within each passing loop until it changes into gas when returned outdoors via another set of coils in exterior units’ fan unit(s).

Types Of Heat Pumps

1. Air-to-Air Heat Pumps: An air-to-air heat pump extracts the heat from the outside air and transfers it to a coolant using an outdoor unit and compressor. The coolant is then circulated through ducts in different areas of the home, allowing for individual climate control in each room and better energy efficiency throughout the property.

2. Air-to-Water Heat Pumps: An air-to-water heat pump uses a more complex process to extract heat from the outside air and transfer it to water, which can be used for heating and cooling. This type of pump is usually installed outdoors near an electrical outlet or other power source and requires careful installation by a professional technician or HVAC contractor. It also requires regular maintenance and service to keep running efficiently.

Advantages And Benefits Of Air To Water Heat Pumps

Air-to-water heat pumps offer impressive energy efficiency, lower operational costs, and improved environmental sustainability compared to traditional heating systems.

Energy EfficiencyAir to water heat pumps typically achieve high energy efficiencies across SEER, HSPF, COP, and EER ratings.
Higher metrics denote increased efficiency and savings.
These systems hold environmental advantages over nonrenewable options such as natural gas furnaces.
Cost SavingsAir to water heat pumps can lead to savings of up to $12 billion per year.
Installation costs and energy bills are typically lower, in many cases about 20% less than other heating methods.
Most consumers experience up to 40 percent lower electricity bills compared to furnaces or boiler systems.
These units can help homes achieve net zero carbon emissions if combined with renewable sources such as solar panels.
Environmental SustainabilityHeat pumps are considered efficient sources of renewable energy.
Air to water heat pumps can reduce carbon dioxide emissions by at least 75% compared to traditional systems.
When combined with other renewable energy sources, the need for traditional fuels is further reduced.
These heat pumps achieve up to five times more cooling energy than electricity used, leading to lower running costs.
Quiet OperationAir to water heat pumps are known for quiet operation, with some brands offering sound outputs below 25dB(A).
Advanced features such as DC Brushless motors can further reduce operational noise.
Improved ComfortAir to water heat pumps can maintain consistent temperatures and reduce humidity levels within a building.
These systems often come with zoning capabilities allowing separate temperature regulation in different areas.
Daikin’s Altherma 3 H Geothermal System, for example, allows temperature preset for up to seven zones.

Disadvantages Of Air To Water Heat Pumps

The drawbacks of air to water heat pump are mentioned in the table below:

Initial CostAn air-to-water heat pump ranges from $3,000 to $6,000, excluding installation expenses and potential rebates. Prices can increase for larger capacities or specialized models. For instance, models designed for pools can reach up to $10,000. Despite high initial costs, long-term benefits make them a good investment. Energy-efficient pumps could save up to $1,000 annually on energy bills for ten years and significantly reduce their carbon footprint.
Climate LimitationsAir-to-water heat pumps may be less efficient in freezing and high humidity conditions. For example, in temperatures below -5°C, efficiency can drop by 10-25%. They can lead to increased energy consumption in such climates to maintain a comfortable indoor temperature. Energy consumption can grow up to 15% in high-humidity areas. These systems may not be suitable in regions with average winter low temperatures below zero or high summertime humidity, such as the US Southeast Coast or the Florida Keys.
Maintenance RequirementsRegular maintenance includes checking, cleaning, and adjusting parts like filters, fans, and cooling coils. This maintenance can cost around $150 to $500 annually, depending on the system’s complexity and local labor rates. Maintenance tasks might include:Changing the air filter every three months.Monitoring refrigerant levels.Cleaning or replacing fan blades.Lubricating motors.Cleaning evaporators/condenser coils.Flushing piping systems.Inspecting electrical connections.Immediate attention should be given to potential issues, such as leaking connections. Paying attention to these issues can lead to further damage and repair costs.

Factors for choosing the right Air To Water Heat Pump

When selecting an air-to-water heat pump, it is essential to consider the size and capacity, brand and manufacturer, maintenance options and service requirements, and climate and location factors.

Size and CapacityOptimal heating capacity is essential for a heat pump’s efficiency, reducing the need for supplemental heating. Physical dimensions: usually up to 3 ft (1m) wide, 3ft (1m) high, and 1ft (300mm) in depth. Source water flow needs 2-3 gallons per minute per ton (12,000 Btu/hr) of heating capacity.The heat pump size should be chosen based on factors such as the space size, insulation level, desired temperature range, and climate zone.Example: A poorly insulated house in a cold climate might need an 8-ton (96k Btu/hr) heat pump system, while a well-insulated place in milder weather might need only a 4-ton (48k Btu/hr) system.Air-to-water heat pumps are commonly used in retrofit markets for their higher efficiency.
Manufacturer and BrandConsideration of reputable manufacturers and brands is vital for ensuring quality and reliable performance.Experienced contractors can provide valuable advice based on their experience with different systems.Factors to consider include the system’s energy efficiency, cost of ownership, warranty on parts, service plans, and dealer support.Researching various brands online can provide valuable insights.
Maintenance and ServiceRegular maintenance ensures the system’s efficiency, optimal performance, and longevity.Maintenance tasks include cleaning, inspection, and proper lubrication by a professional technician every year.Filters should be checked and replaced, if necessary, every three months.Regular servicing can help identify and rectify potential issues before they become significant problems.An air-to-water heat pump that is properly maintained can last up to 20 years or more, providing efficient heating and cooling comfort all year round.
Climate and Location ConsiderationsAir source heat pumps require temperatures above 40ºF (4.44ºC) to function effectively, limiting their suitable locations.They are only suitable for locations with high humidity or extreme cold if a two-stage system is used.They require 1,000 cubic feet of space per ton of output, which can limit their use in densely populated urban areas.To ensure optimum performance and avoid noise issues, a minimum distance between interior and exterior components should be maintained, and noise buffers or walls may need to be installed.

Installation And Maintenance

Correctly installing an air-to-water heat pump system is essential to ensure its optimum performance. A certified technician should always be consulted for the installation of these systems and for their ongoing maintenance to maintain their efficiency and lower running costs.

Proper Installation Considerations

Various factors should be considered for a successful installation process when installing an air-to-water heat pump system.

  •  Line sets must be suitably sized and insulated to ensure efficient heat transfer between the indoor and outdoor units. 
  • Additionally, the power supply is essential. Ensure it’s rated sufficiently to provide enough power for all components in the system. 
  • It’s also essential to consider the climate while installing an air-to-water heat pump, as some systems may have lower efficiency ratings in cold temperatures.
  •  Last but not least, if the home has an existing internal heating setup, additional considerations may be necessary so that these systems work seamlessly together with the new air source unit.

Installation guidelines can help simplify this part of the installation process:

  1.  Select line sets that are correctly sized for your particular refrigerant and application standard sizes range from ¾ inch up to 3 ½ inches;
  2.  Insulate piping runs at least 6″ beyond where they pass through exterior walls or floors;
  3.  Make sure an adequate power supply is available from a dedicated circuit breaker. Before starting any wiring work, verify whether you need a single-phase (208/230 volts) or 3-phase wiring.
  4. Install outdoor units away from obstructions such as trees, buildings, and fences. One fundamental rule of thumb here is allowing 18 inches of clearance on each side of the outdoor unit;
  5.  Use toe-kicks set beneath your wall mount, cooling indoor users when mounting them onto interior walls. Note, though, que this may vary depending on the manufacturer’s recommended product placement guidelines;
  6.  Where possible, add anti-vibration dampers during pipe runs which will reduce any noise created by pipework movement over time inside walls or ceilings/rafters above equipment locations. Check the manufacturer’s recommendations before completing the installation. 
  7. Lastly, Inspect refrigerant lines numerous times during the installation to ensure they are secure without crimps, kinks, or leaks presented before the inviting system with potentially destructive gasses. If a home already has an existing internal heating system, consult all relevant consultants, engineers, or designers who specify how interactional both types of designs are.

Maintenance Tips And Guidelines

Several preventive maintenance tips and guidelines should be followed to ensure the efficient operation of air-to-water heat pumps.

Develop a preventative maintenance plan which includes regular seasonal inspections before and after winter and summer, respectively.

Ensure all elements such as fans, condenser coils, indoor unit filters, and other moving parts are constantly well lubricated to avoid putting extra pressure on the system. This also helps reduce noise levels too.

Keeping outdoor units free from dirt, leaves, branches, and more can help improve efficiency while reducing the risk of malfunction. This can be done by simply hosing down the outdoor unit regularly or using air blowers if available.

Inspect all ducts, pipes, or wiring for cracks or holes and repair them where possible to reduce lost energy in the system.

Regularly check indoor thermostat settings so that heating or cooling temperatures remain within recommended ranges for maximum efficiency.

Clean or replace air filters monthly to avoid build-up of dust and dirt, which can impair air quality and increase energy bills due to increased running time hours needed by the system to operate at optimum performance levels.

Have your systems inspected yearly by a certified HVAC technician who’ll give you professional advice, such as routine cleaning options, removal of blockages masking essential parts, etc., to keep your system running smoothly.

Applications Of Air To Water Heat Pumps

Air-to-water heat pumps are used widely in home heating and cooling, pool and spa heating, and commercial and industrial applications.

Residential Heating and CoolingAir-to-water heat pumps provide residential heating and cooling by transferring heat from outside air to water. These systems can drastically reduce energy bills due to their high efficiency compared to traditional HVAC systems. Different types include geothermal pumps (ground or water source) and air-source pumps, suitable for colder climates. Air-sourced models are ideal for residences that lack easily accessible geothermal resources, combining cost efficiency, renewable energy utilization, and low noise levels for optimal comfort.
Commercial and Industrial Heating and CoolingAir-to-water heat pumps offer advanced heating and cooling solutions for commercial and industrial buildings. They capture heat from the outside air and transfer it inside, providing either hot or cold air as needed. These systems are more energy-efficient than traditional HVAC systems that burn fuel, offering significant cost savings. Air to Water Heat Pump systems are eco-friendly as they don’t require combustible fuels. With proper installation, these systems are highly reliable and require minimal maintenance.
Pool and Spa HeatingAir-to-water heat pumps are an effective solution for heating swimming pools and spas. They extract thermal energy from the air or ground, converting it into hot water for heating pools. Compared to traditional solar heaters, these pumps offer higher output temperatures, making them ideal for larger bodies of water like indoor swimming pools. Their operation based on square law curves ensures maximum efficiency under optimal conditions. Heat transfer occurs via pipes connected throughout the pool or spa area with embedded plates made from high-quality stainless steel, which offers corrosion resistance against chlorine water.

Hydronic Heating And Cooling With Air To Water Heat Pumps

Hydronic heating using air-to-water heat pumps can provide a wide range of energy-efficient and cost-effective solutions for residential, commercial, and industrial applications.

Understanding Hydronic Heating

Hydronic heating and cooling systems feature a network of pipes with liquid water circulating through them, creating a comfortable temperature environment in all building parts.

Water is heated or cooled and sent through the pipes to individual rooms. This technology can be used alone but is often accompanied by an air-to-water heat pump for increased efficiency and improved comfort.

The heat pump works similarly to other pumps, transferring energy from one source to another. In this case, it utilizes free low-value ambient air as its primary energy input while providing backup thermal power when natural sources are unavailable, like on cold winter days.

An air-to-water heat pump connected to hydronic systems provides better temperature control throughout the home while being more environmentally friendly than traditional HVAC designs since they reduce carbon dioxide emissions that contribute to climate change.

The installation process requires minimal disruption since most components are installed indoors, such as wall-mounted geothermal units or floor models; no outdoor piping is necessary during initial setup, only thermally insulated underground loops tubing, which provides good UV shielding against corrosion and leaks over time, ultimately resulting in a greater lifespan of your system.

Benefits And Advantages

Air-to-water heat pumps feature significant advantages compared to traditional HVAC systems. Unlike typical air conditioning systems, hydronic heat pumps can transfer 300% more energy than they create as they are able to move the existing ambient heat instead of creating it.

This is why they have around 70% less electricity usage than electric baseboards when used for heating and cooling solutions. Not only that, but since these pumps only use electricity to cool or warm a space, their energy consumption is much lower compared to those heated with central furnaces.

In addition, modern air-to-water heat pumps offer both heating and cooling capabilities while also being considered an emerging renewable energy source all without breaking the bank due to their relatively low initial cost.

Moreover, when combined with a hydronic distribution system such as in floor radiant heating circuits or radiators and fan coils, this type of technology can be used for both home hydronic heating and cooling making them even more efficient from an environmental standpoint.

Air To Water Heat Pumps In Action

Real-life examples and case studies of air-to-water heat pumps in action can be found across various commercial applications and residential properties.

Real-life Examples And Case Studies

One of the most successful and well-documented case studies of air-to-water heat pumps was that of P. Carroll in 2019 when they installed an ASHP system in a home in Northern Ireland.

The study assessed this heating system’s accuracy, energy efficiency, and comfort level. The results showed that despite having low thermal conductivity properties compared to traditional hot water systems, ASHPs could maintain internal temperatures at almost the same level as other heating solutions due to their high collection power.

The Hubbards-Nelsons have also adopted an Air Source Heat Pump (ASHP) for their Concord home in Massachusetts after noticing significant gains from switching from a natural gas-heated HVAC system. They now have nearly 35% monthly savings on average energy bills showing how cost-effective these systems can be while helping save the environment by reducing its carbon output by burning fewer fossil fuels than other traditional solutions available today.


Air-to-water heat pumps offer an efficient way of heating and cooling a building while providing potential cost savings in energy bills. They are ideal for residential, commercial, industrial, pool, or spa applications.

By providing efficient heating or cooling and hot water on-demand, they can reduce the need for other types of heating equipment like boilers or electric radiators. As technology continues to advance and more manufacturers explore ways to maximize efficiency from existing systems, air-to-water heat pumps are expected to become even more reliable, effective, environmentally friendly, and cost-effective in the near future.

For instance, newer hybrid models combine traditional oil-based HVAC units with air-source heat pump systems for greater efficiency. This is particularly advantageous in cold climates where normal ASHPs struggle during winter months.

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