This study explores the principal modes of high-pressure transcritical channel flow from direct numerical simulation data. The four cases investigated correspond to CO_2 at high-pressure conditions (P/P_c = 1.5) confined between a cold/bottom wall (T/T_c=0.8 - 0.95) and a hot/top wall (T/T_c=1.1 - 1.4). The bulk velocity ranges between U_b = 0.5 - 1.0{m/s} with corresponding bulk Reynolds numbers of Re_b approximately between 1000-2500. In laminar cases, energy is predominantly concentrated in the initial modes, with approximately 95% of the energy captured by the first mode. Conversely, turbulent cases exhibit a broader distribution of energy across multiple modes, necessitating 50 to 100 modes to encapsulate the system's key characteristics. This disparity underscores the multiscale phenomena inherent in turbulent flows. Furthermore, thermodynamic variables in turbulent regimes demonstrate slower energy decay, particularly in later modes, indicating complex flow structures. These findings emphasize the necessity for detailed thermodynamic modeling to accurately capture the flow dynamics in high-pressure transcritical environments.