For software that does not calculate an annual distribution system efficiency (DSE) for cooling, the DSE may be approximated by equation 3.4.i in ANSI/BPI-2400-S-2012: Standard Practice for Standardized Qualification of Whole-House Energy Savings, Predictions by Calibration to Energy Use History. Enter values as a fractional number between 0 and 1, i.e. 80% = 0.8