The heating and cooling load of a HVAC system is the amount of energy required to maintain a comfortable indoor environment. It is determined by the size of the space, the number of occupants, the type of equipment used, and the climate. The heating load is the amount of energy required to heat the space, while the cooling load is the amount of energy required to cool the space. The total heating and cooling load of a HVAC system is the sum of the two. To calculate the heating and cooling load, a professional HVAC technician will use specialized software to analyze the space and its occupants. This analysis will take into account factors such as insulation, air infiltration, and solar gain. The technician will then use this information to determine the size and type of HVAC system needed to meet the heating and cooling load requirements.