ISO 1217 recognised isentropic efficiency as the best way to compare the energy performance of compressor systems. One key challenge remains: the standard does not yet provide a clear, step-by-step procedure that testing laboratories around the world can apply consistently—especially under different ambient conditions.

To address this, EMSA conducted an international round robin testing programme, exchanging two commercial, packaged electric motor-driven screw compressors between three laboratories worldwide. The work compared:

• interpretations of ISO 1217 requirements,
• compressor setup approaches,
• choices of suitable electrical and pneumatic measurement instruments, and
• processing of the measurements made.

The report includes the test results and a practical guide for measuring specific energy and isentropic efficiency of packaged air compressors in line with ISO 1217:2009 and Amendment 1:2016 — supporting both users and regulators in performance comparisons.

An Excel-based calculation tool, the EMSA Compressorcalc, was also developed to perform the stepwise calculation of isentropic efficiency based on test results as specified in ISO 1217 Annex C and Amendment 1.

With this, EMSA intends to contribute toward more transparent, comparable, and robust compressor efficiency testing worldwide.