Proposal to amend UN GTR No. 21 on determination of system power of hybrid electric vehicles and pure electric vehicles with more than one electric machine for propulsion. The amendment establishes reference points representing where mechanical power is first produced from energy storage systems, distinguishes between Test Procedure 1 (measuring electrical power and engine power) and Test Procedure 2 (measuring torque and speed at axles or wheel hubs), requires manufacturers to provide verifiable K factors representing conversion efficiencies, mandates five test repetitions with averaging of the last four, specifies measurement accuracies and frequencies, removes dynamometer roller measurement option for TP2 in favor of torque and speed sensors or hub dynamometer, adds system bench testing as alternative with manufacturer approval, and includes applicability guidelines determining which procedure applies to specific powertrain architectures.