To improve building energy efficiency, the development and use of HVAC power density (HvacPD) allowances could be a powerful tool for improving building efficiency. In a format similar to the lighting power density (LPD) values that appear in ANSI/ASHRAE/IESNA Standard 90.1-2004, Energy Standard for Buildings Except Low-Rise Residential Buildings, HvacPDs would be set in terms of electrical power input per unit area (W_e /ft² [W_e /m²]) for the entire HVAC system.