A coupled model of a generic bus and an all-fresh air Heat Pump (HP) system was developed to investigate the impact of the cabin set-point temperature on the thermal comfort level and the energy consumption of heating. Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) from Fanger's model were used to quantify the comfort level inside the cabin. Different heating strategies based on fixed and variable set-point temperature were examined for an all-fresh air HP under different outdoor temperatures. The results indicate that for the studied all-fresh air HP, adopting a proper heating strategy based on variable set-point temperature could reduce the power demand up to 61% when the outdoor temperature is -5 °.