{"id":57446,"date":"2026-09-29T16:07:53","date_gmt":"2026-09-29T15:07:53","guid":{"rendered":"https:\/\/ecoforest.com\/?p=57446"},"modified":"2026-09-29T16:07:53","modified_gmt":"2026-09-29T15:07:53","slug":"how-air-source-heat-pumps-work-step-by-step","status":"publish","type":"post","link":"https:\/\/ecoforest.com\/en\/news\/how-air-source-heat-pumps-work-step-by-step\/","title":{"rendered":"How Air-Source Heat Pumps Work, Step by Step"},"content":{"rendered":"\n

Air-source heat pumps work by extracting heat that already exists in the outdoor air\u2014even when it is cold\u2014and transferring it into your home for heating, cooling and hot water. They do not generate heat by burning fuel: they move<\/strong> it using a heat pump and a refrigerant that circulates in a closed loop. That is why they are so efficient: for every unit of electricity they consume, they deliver several units of thermal energy.<\/p>\n\n\n\n

In this guide, we explain step by step, with a diagram, what happens inside an air-source heat pump, why it achieves such high performance and the role each component plays.<\/p>\n\n\n\n

What is air-source heat pump technology, and how does it work?<\/h2>\n\n\n\n

Air-source heat pump technology harnesses the thermal energy in the air<\/strong> using an air-to-water heat pump<\/strong>. Even when air seems “cold”, it contains heat energy at temperatures well below freezing. A heat pump can capture that energy, concentrate it and raise it to a temperature suitable for heating your home.<\/p>\n\n\n\n

The key is a well-known physical principle: when a fluid (the refrigerant) changes state\u2014from liquid to gas and from gas to liquid\u2014it absorbs or releases large amounts of heat. Air-source heat pump technology uses these changes of state in a closed circuit to move heat from outside to inside (in winter) or from inside to outside (in summer).<\/p>\n\n\n\n

The heat pump cycle: 4 steps<\/h2>\n\n\n\n
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Everything revolves around four components that form a closed circuit through which the refrigerant circulates. Here is the complete process:<\/p>\n\n\n\n

Step 1 \u00b7 Evaporator: the refrigerant captures heat from the air<\/h3>\n\n\n\n

In the outdoor unit, the refrigerant arrives as a liquid at a very low temperature, colder than the surrounding air. As it passes through the evaporator<\/strong>, outdoor air\u2014moved by a fan\u2014transfers its heat to the refrigerant. That energy causes the refrigerant to evaporate and become a gas<\/strong>.<\/p>\n\n\n\n

Here is the clever part: because the refrigerant is colder than the outdoor air, it can capture heat even in the depths of winter.<\/p>\n\n\n\n

Step 2 \u00b7 Compressor: the energy is concentrated<\/h3>\n\n\n\n

The refrigerant gas, still at a low temperature, enters the compressor<\/strong>, the heart of the system. Compressing it raises its pressure and, with it, its temperature increases dramatically<\/strong>. This is the only point in the cycle where a significant amount of electricity is consumed, and it is what makes it possible to “raise” low-temperature heat to a level useful for your home.<\/p>\n\n\n\n

Step 3 \u00b7 Condenser: heat is transferred to your home’s water circuit<\/h3>\n\n\n\n

The hot, high-pressure gas reaches the condenser<\/strong>, a heat exchanger where it transfers its heat to the home’s water circuit<\/strong>. As it loses energy, the refrigerant cools and condenses back into a liquid<\/strong>. The heat transferred to the water is what ultimately supplies your heating system.<\/p>\n\n\n\n

Step 4 \u00b7 Expansion valve: back to the beginning<\/h3>\n\n\n\n

The liquid refrigerant, still under pressure, passes through the expansion valve<\/strong>, which sharply reduces its pressure and temperature. This makes it colder than the outdoor air again, and the cycle starts over<\/strong>, continuously.<\/p>\n\n\n\n

Why are air-source heat pumps so efficient? COP explained<\/h2>\n\n\n\n

A heat pump’s efficiency is measured by its COP<\/strong> (Coefficient of Performance): the ratio between the thermal energy it delivers and the electricity it consumes. Because an air-source heat pump moves<\/em> heat instead of generating it<\/em>, it can deliver around 3 to 5 kWh of heat<\/strong> for every kWh of electricity consumed, depending on conditions.<\/p>\n\n\n\n

To assess actual performance over an entire season, the SCOP<\/strong> (seasonal COP) is used. It accounts for temperature variations throughout the year. The milder the climate and the lower the flow temperature your system needs, the greater its efficiency.<\/p>\n\n\n\n

Category<\/th>Gas\/oil boiler<\/th>Air-source heat pump<\/th><\/tr><\/thead>
Energy source<\/td>Fuel combustion<\/td>Heat from outdoor air<\/td><\/tr>
Typical efficiency<\/td>Below 100%<\/td>Delivers several times the energy consumed<\/td><\/tr>
Direct emissions<\/td>Yes (CO\u2082)<\/td>No (at the point of use)<\/td><\/tr>
Functions<\/td>Heating and domestic hot water<\/td>Heating, cooling and domestic hot water<\/td><\/tr>
Operating cost<\/td>Linked to fuel prices<\/td>Linked to electricity prices<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Air-to-water: how heat reaches every room<\/h2>\n\n\n\n

Ecoforest’s air-source heat pumps are air-to-water<\/strong>: the heat captured is transferred to a water circuit that can distribute it in several ways, depending on your system:<\/p>\n\n\n\n