An air to water heatpump is very similar to an external unit of an air conditioner. It is made up of a fan and copper coils circulating refrigerant using a compressor. The heated/cooled refrigerant is used to heat or cool water which is circulated around the underfloor heating or radiator pipework within the villa.
Heatpumps maintain a very high efficiency due to their ability to use the ambient air temperature and concentrate it into heat/cold within the house. Once your build reaches over 200m2 it makes so much commercial sense to use a combination of fancoils and underfloor heating that this becomes the only real option to heat and cool your villa.
When our customers come from cooler climates the average temperature and sunlight hours of the Algarve is often overlooked and they favour technologies such as geothermal heating but it is the high average temperature of the Algarve which makes it absolutely ideal for air-to-water technologies which rely on the ambient air temperature for its efficiencies. The case for geothermal which gives little more efficiency benefit for almost double the capital cost and complexity seems a lot less compelling.
Heatpumps, like air conditioners, come in two main types - Inverters and Non-Inverters. Like air conditioners non-inverters are cheaper to buy but are less efficient (but still more efficient than gas!) as they cannot vary the speed of the compressor which means they are either OFF or ON - they usually require a "buffer" tank to reduce the amount of stop-starts to maintain efficiency. Inverters are more expensive to buy but their variable speed compressor is more efficient and they have far more tolerance with the use of buffer tanks.