The significance of form in green building design is well recognized, as it has a substantial impact on both energy performance and construction cost. This study investigates the impact of the U-shaped plan on the energy demand, which can be flexibly applied to irregular site forms and clustered building blocks, and is widely used in existing office buildings. Specifically, we select the U-shaped plan as the object of study and collect related case data primarily from Hangzhou and Shanghai. Using Python, we generate plans based on two lengths, two angles, and depth, which serve as basic parameters and boundary conditions. The EnergyPlus platform is utilized for dynamic simulation of the energy consumption of each model, and correlation analysis using the Spearman coefficient method identifies two planar factors (depth-length ratio and modified length) that have the most significant influence on energy consumption, including five basic parameters. Regression fitting and regression evaluation of the model further identify morphological critical information in the plan. Our research reveals that the critical interval of depth-length ratio (M1) is in (0.48, 1.02), and the critical point of the modified length (M2) is 109.38 m. Furthermore, the contour plot of M1–M2–E1 is obtained, illustrating the mutual trend between morphological parameters (M1 and M2) and annual energy use intensity, which serves as a useful aid for designing low energy consumption solutions.