Coefficient of Performance (COP) of the electrical chiller is defined as:

The Coefficient of Performance (COP) is a critical metric in EDGE for assessing the energy efficiency of chillers, a common green building design element. The EDGE Methodology Report defines COP for electrical chillers: "The Coefficient of Performance (COP) of an electrical chiller is defined as the ratio of thermal output (cooling provided, measured in kW) to electrical input (power consumed, measured in kW). A higher COP indicates greater efficiency, as more cooling is produced per unit of electricity" (EDGE Methodology Report Version 2.0, Section 5.1: Energy Efficiency Metrics). Option B, thermal output / electrical input, matches this definition directly. Option A (thermal output / thermal input) is incorrect, as it applies to heat-driven systems like absorption chillers, not electrical ones. Option C (electrical input / thermal output) inverts the ratio, representing the inverse of COP. Option D (electrical output / electrical input) is irrelevant, as chillers produce thermal output, not electrical output. The EDGE User Guide reinforces this: "For air-cooled and water-cooled chillers, COP is calculated as thermal output divided by electrical input to evaluate energy efficiency" (EDGE User Guide, Section 4.2: Energy Efficiency Measures).