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How Does a Hydronic Air-to-Water Heat Pump Work?

Views: 149     Author: Site Editor     Publish Time: 2023-05-04      Origin: Site


Are you looking for ways to warm your residence or office space without blowing a hole in your budget? Consider a hydronic heat pump, aka an air-to-water heat pump. This innovative technology is gaining popularity in several regions of the world, and it offers a wide range of benefits, including superior temperature control with lower operating costs and greenhouse gas emissions.

It’s easy to install in modern or old homes without excruciating disruptions and generates less noise than standard air conditioners. Indeed, it’s a more cost-effective and eco-friendly way to keep your home or commercial building's energy costs down.

What is a hydronic (air-to-water) heat pump?

A hydronic heat pump is an air-source heat pump that extracts heat from the air outside a building and distributes it in the interior via a hydronic heating system. It’s called a hydronic system because it uses water to distribute heat.

The heat extracted from the exterior is used to heat water, which is then sent through baseboard or floor tubing, releasing heat to underfloor heating systems. These could be radiators, trench convectors, heated towel rails, or panel radiators.

Conversely, when the temperatures inside a building get too high, the heat pump extracts the excess heat and sends it outside via the same system. Thus, a hydronic heat pump can heat and cool buildings, including homes and commercial structures, and also provide hot water for domestic use.

What are the parts of an air-to-water heat pump?

Air-to-water heat pumps usually feature an indoor unit and an outdoor unit. These comprise a compressor, condenser, expansion valve, evaporator, and refrigerant. During the winter, the outdoor unit extracts heat from the air outside a building for use in the interior.

The technology has been designed to absorb heat even when temperatures fall as low as -15 Celsius. On the other hand, the indoor unit absorbs excess heat from a house during warm seasons, allowing the interior to remain cozy.

How does an air-to-water heat pump work?

The working principle behind an air-to-water heat pump is based on the refrigeration cycle, which typically starts with compression, condensation, and expansion, followed by evaporation.


When the interior of a building needs warming, the refrigerant absorbs heat from the exterior air, turning it into gas or vapor. The gas or vapor then goes through the compressor, where its pressure and temperature increase rapidly. This compressed refrigerant then passes through a heat exchanger, transferring its heat to the water in the hydronic system.


After distributing heat to the hydronic system, the gas or vapor goes through a condenser, turning into a liquid again.


When the inside of a building needs cooling, the condensed refrigerant passes through an expansion valve designed to rapidly decrease its pressure so it can evaporate and absorb heat from the indoor air.

Ultimately, the refrigerant returns to the outdoor unit, and the cycle starts again. Ultimately, this continuous process absorbs and distributes heat, ensuring the inside of a house remains cozy no matter the prevailing weather. It can also provide hot water for domestic use.

How Efficient is a Hydronic Heat Pump?

Of course, before deciding on a heat pump, you’ll want to know if it will help reduce your energy bill. For heat pumps, this simply involves checking the efficiency, aka coefficient of performance.

It’s a measure of a system’s heat output vis-a-vis energy input. Obviously, the higher the COP, the more efficient a hydronic heat pump unit is. Most air-to-water heat pumps come with COPs between 3 and 4.

That means that for one kilowatt of electricity, there are 3–4 kilowatts of heat load. This is way more powerful than wood-fired stoves, gas boilers, and electric boilers, which typically have COP ratings below 1. In fact, here is a look at the advantages of a hydronic heat pump.

Energy efficient

As already mentioned, hydronic heat pumps use less energy to output the same heat load as electric, gas, or wood-fired heating systems. Hydronic heat pumps don’t generate heat; they simply move it. On the other hand, traditional systems need to generate heat, increasing energy costs and environmental costs.

Affordable to operate

Operating a heat pump is cheaper than operating electric, gas, or wood-fired heating systems. Indeed, research shows that it takes around $1500 to run a heat pump at a 20-kilowatt heat load for 960 hours spread over 120 days in a 200-square-meter building.

On the other hand, using an electric boiler in a similar house for the same duration will cost you around $5000. The relative running costs for wood-fired and natural gas systems are $2200 and $1800, respectively.

Use less electricity.

Air-to-water heat pumps use less electricity as a power input. In fact, they use 60% less electricity compared to a standard electric water heater. Furthermore, an off-grid residence incorporating a solar power system to produce electricity will result in greater savings, let alone environmental benefits. To run a 300-litre hydronic heat pump in a standard-sized.

At home, you’ll need just around 3.5 kilowatt hours per day of electricity, which most solar panels can comfortably generate depending on your location. Plus, heat pumps can be programmed to extract and store heat during the warmest hours of the day. This simply means that the heated water is stored in underfloor water tanks for later use.


Heat pumps make an indoor space cozy no matter the prevailing climate. Air has heat even when it's at -15 Celsius. Therefore, heat pumps remain efficient even when external conditions get dreary.


As mentioned, air-to-water heat pumps are designed to warm a house as required or cool it when it gets exceedingly hot. This ensures year-round comfort and eliminates the need to buy separate heating and cooling systems. Furthermore, they can help meet a home’s hot water needs.

Even heat distribution

Hydronic heat pumps distribute heat evenly since water is their primary heat distribution medium. Water is an excellent heat conductor because it can carry 4000 times more heat than air. However, it takes more energy to raise the temperature of water, which is an advantage as it makes it easier to regulate the rate at which a hydronic heat pump warms or cools a house.

Additionally, air-to-water pumps don’t heat air directly; they heat objects in a room via radiation. This helps ensure a consistent and even heat distribution. Also, most heat pumps come with thermostats that help direct heat to different home areas, removing cold spots.


Air-to-water heat pumps reduce carbon and noise emissions. As already mentioned, heat pumps use less electricity than traditional heating systems. Plus, it really helps to cut your property's carbon footprint if you augment the power input with solar energy.

Also, heat pumps won’t disturb your home or sleep because they are much quieter than standard heating systems.

Low maintenance

Another advantage of air-to-water heat pumps is that they require low maintenance. They have fewer moving parts than the conventional heating system. The advantage here is that they are less likely to break down due to factors like friction.

Thus, you won’t have to incur frequent repair costs, leaving you with money to save. Plus, the lack of many moving parts increases the equipment’s lifespan. Indeed, a high-quality heat pump can provide up to 20 years of service.

What are the application areas of a hydronic heat pump?

You can use air-to-water heat pumps in a home, industrial, or commercial setting. Here’s a breakdown:

Residential heating and cooling

Hydronic heat pumps can be integrated with residential radiators, trench convectors, heated towel rails, or panel radiators to heat up or cool a home, depending on the weather condition. They can also help homes meet their hot water needs.

Pool heating

As mentioned, hydronic heat pumps can help a property meet its hot water needs, including for pools. The hot water in the hydronic system can be moved to a pool, allowing residents to enjoy a heated pool even when the weather is freezing.

Commercial heating and cooling

Air-to-water heat pumps can also be used in schools, hotels, hospitals, offices, and other commercial setups to provide efficient heating and cooling all year round.

Industrial heating and cooling

Industrial settings where air-to-water heat pumps can be used include workshops, warehouses, and manufacturing and fabrication plants. These systems can provide heating and cooling, ensuring indoor conditions remain cozy for workers.


Heating and cooling can comprise at least a third of a property’s energy use. With skyrocketing electricity and gas prices, you should try looking into alternative heating and cooling systems like a hydronic heat pump for your property. A hydronic heat pump uses at least 60 percent less power to generate the same heat load as traditional heating systems.

It’s eco-friendly, cheap to operate and maintain, and can be installed in new and old homes without too much hassle. Get in touch with SPRSUN for high-quality heat pumps. We have been in the global heat pump market for over 25 years and supply EN14511 standard heat pumps with CCC, CB, CE, SAA, ROHS, ERP, TUV, and KEYMARK certifications. Let our team help you find the right air-to-water heat pump for your property.

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