When to use: Use to benchmark the efficiency of a chilled-water plant. Sum the electrical demand of the chiller, cooling tower fans, condenser water pump, and chilled water pump, then divide by the cooling load in tons to get kW/ton (lower is better). A well-tuned all-variable-speed water-cooled plant targets ≈ 0.5–0.7 kW/ton. Because efficiency degrades at low load, set the part-load ratio (PLR) to estimate kW/ton at the operating point.