Heating load and cooling load are two terms used to describe the amount of energy required to heat or cool a space. Heating load is the amount of energy required to raise the temperature of a space to a desired level, while cooling load is the amount of energy required to lower the temperature of a space to a desired level. Both heating and cooling loads are determined by factors such as the size of the space, the insulation of the space, the number of occupants, the climate, and the type of HVAC system used. The heating and cooling loads must be accurately calculated in order to properly size and install an HVAC system.