The COOMET.EM-K5 Key Comparison of Power was carried out in the CIPM–MRA framework from 2016 to 2018. The main aims of this project were to compare national measurement standards of low-frequency 50/60 Hz power and to link with the CCEM-K5 Key Comparison. This comparison was carried out between 13 National Metrology Institutes which are the members of five Regional Metrology Organisations: COOMET, EURAMET, APMP, GULFMET and AFRIMET. The selected travelling standard of low-frequency 50/60 Hz power was compared at: UMTS (Ukraine), BelGIM (Belarus), VNIIM (Russia), GeoSTM (Georgia), CMS (Kyrgyzstan), UME (Turkey), SMU (Slovakia), LEM-FEIT (R. Macedonia), NIM (China), MASM (Mongolia), QCC EMI (UAE), SASO-NMCC (Saudi Arabia), and NIS (Egypt). UMTS was a pilot laboratory. NIM (China) and VNIIM (Russia) were linking National Metrology Institutes for the linking process between CCEM-K5 Key Comparison and COOMET.EM-K5 Key Comparison due of participating in CCEM-K5 Key Comparison.The paper is devoted to the discussion of issues concerning the participation and further evaluation of measurement data of COOMET.EM-K5 Key Comparison of Power. Main results of participating laboratories measuring the same power of travelling standard of low-frequency 50/60 Hz power in a framework of COOMET.EM-K5 Key Comparison of Power are presented. Besides, the paper describes some problems concerning the evaluation of travelling standard drift effect and its further influence on evaluation of Key Comparison Reference Value during a Key Comparison. Degrees of Equivalence and Expanded Uncertainties of National Metrology Institutes participants are set. In addition, En number was calculated for each National Metrology Institute participating in COOMET.EM-K5 Key Comparison of Power with the aim of determining data consistency.