Italy is one of the largest heating markets in Europe and has a very important tradition in the field of gas-fired condensing boilers. In order to counter the recent expansion of the air-to-water (ATW) heat pump market, Italian traditional combustion heating equipment man- ufacturers rapidly created a new emerging market for hybrid heating, ventilation, and air conditioning (HVAC) systems, which are supplied as unique systems normally based on the following three components: