In 1902, Willie H. Carrier invented the first electrically driven chiller for air conditioning (AC). Since then, assorted figures of merits (FOMs) were used for energy efficiency evaluation, assuming parity between all types of derived energy consumed. Such practices of interpreting FOM expressions are deemed thermodynamically incomplete, as the units of energy conveyed merely the quantitative aspects, ignoring its embedded qualitative potential. The quality exclusion in derived energy has plagued the chiller industry since its inception with a numerical oddity, i.e., the useful output (kWh cooling) of chillers is found greater than the input (kWh electricity or thermal). Pedagogically, the incongruity defies the Laws of Thermodynamics of any cycle because all real chillers incurred much dissipation. Rationally, the energy efficiency must always be less than unity unless there exists a fundamental abnormality. At this juncture, a standard primary energy (QSPE) platform is proposed for all FOM expressions of chillers. Invoking the classical heat engines and the Carnot work associated with the derived energy, its equivalent QSPE at a common primary energy platform can be correlated via the corollary of the Laws of thermodynamics. By assigning the QSPE to both the input and output expressions of chiller FOM, namely the Coefficient of Performance (CoP), an accurate universal efficiency is formulated, resolving the said misconception and ensuring the laws of energy conservation within a cycle are observed. Henceforth, the chillers’ efficacy expression returns to its normalcy where its ratio always less than unity. In addition, the causal efficacy development enables designers and users to intuitively improve the aspects of design and optimal rating regimes of chillers. The methodology ensures a better understanding of chillers’ performance needed of AC towards a sustainable cooling future.