Air-to-water heat pump pros and cons

All you need to know about air to water heat pump system

Heat pumps are mechanical devices that work in line with physical laws, using such phenomena as evaporation and condensation to transfer heat from elsewhere outside the walls of your house inside. In the next section, we will consider the physics in details, while now let’s get into details what are heat pumps and their difference from furnaces.

When you use a furnace, you have to burn a gas, fossil fuel or wood/pellets inside it in order to obtain heat that would be transferred due to heat interchange process to water/other liquid circulating in your home heating system. With this, a lot of heat is produced and a combustion process completely destroys the source of this heat.

It is not the case with heat pumps: they do not destroy the source of heat and only extract some part of heat inherent to it. Answering the question how does an air to water heat pump work we must come to see the following diagrams.

How it works

how does an air to water heat pump workhow does an air to water heat pump work

As you can see from these pictures, a cycle of condensation and evaporation makes the process work for heating up your dwelling. When a liquid in pipes of a heat pump absorbs heat from elsewhere (depending on a type of your heat pump, it may be air, ground or water), it collects it in the system waiting for some critical point to occur when the liquid (water or other substance) evaporates. At this point, the collected heat is distributed through a number of molecules in the gaseous substance in pipes. When it goes to your house, it condenses and releases heat during this moment, saturating your dwelling with heat taken from outside and transferred to you. Within some time, such saturation makes the indoor temperature rise to appropriate levels set by you. Liquid condensed in a device named condenser and evaporates in an evaporator, accordingly, thanks to laws of physics and some electricity to run.


Air to water heat pump efficiency depends on many factors, such as:

  • how big house it has to warm up
  • what is the temperature set as regular indoors and how often does it change
  • is it also used as a heater to sanitary water or just heats premises
  • how powerful a pump is
  • how well the house is insulated: walls, windows, roof, basement, etc.
  • what season of the year is now
  • is it used as a main and only heating system or is it just an auxiliary one.

As you can see, there is a vast list of obvious conditions, in addition to such ones that are even more individual:

  • do you have the own electricity producing cycle (like solar panels or wind generators) or use electricity received from the global network (if yes, it’ll lower your energy bill to zero)
  • do you have the ‘smart house’ system installed or not (if yes, it smoothens the consumption of heat during the time of the day when everyone is gone off the house that lowers the electricity amount required to run a heat pump).

For instance, if to make air to water heat pump system comparison even of the same model and manufacturer between two households, it may turn out that they range on 40% and even more. That is why, usually during calculations, it is adopted to apply the so-called pre-calculated Coefficient Of Performance (COP) that in air pumps is close to 2.4-2.6. It means that on every unit of consumed electrical energy required for work, it gives out 2.4-2.6 units of heat. For instance, COP of water pumps is close to 3-3.5, COP of ground pumps is close to 4-4.5. Some exotic heat pumps may have COP over 5.0 but they are professional models used in large factories or enterprises and too costly and powerful to be installed for individual households.

Air to water heat pump seasonal efficiency ranges. The precise data depends on the average seasonal temperature, but it is lower during the winter and better during summer, obviously. If we take into account the UK as an example close to all of us, it is hard to find a place where heat pump would not operate at all, as even average winter temperature is about +4 °C, while heat pumps operate normally to -6 °C and even to -20 °C with additional equipment. In winter, COP can be close to 1.0-1.4, while in summer it can be 2.3-3.1.

How to install an air to water heat pump

Installation process must be done exclusively by a certified company, as there are tons of nuances during this procedure. Unless you don’t want to lose your production guarantee.

All figures and numbers are approximate and stated for information only. Figures for your property may vary. Subject to survey.

Heat pumps 293

Air-to-water heat pumps pros and cons