This study conducted a thorough evaluation of an improved dendritic learning (DL) framework, focusing specifically on its application in power load forecasting. The objective was to optimise the activation functions within the synapses and somas of DL to enhance their adaptability across diverse real-world scenarios. Through a rigorous analysis involving 25 experiments across five activation functions (sigmoid, hyperbolic tangent (tanh), rectified linear unit (ReLU), leaky ReLU, and exponential linear unit (ELU)), we elucidated their impacts on both regression and classification performance. Notably, the leaky ReLU–tanh combination demonstrated exceptional mean performance and effectiveness across 14 benchmark datasets from the University of California Irvine Machine Learning Repository, surpassing alternative combinations. When applied to power load forecasting, this combination outperformed other models, particularly transformer and LSTM. These findings underscore the significant advantages of the leaky ReLU–tanh-based DL framework in accurately predicting electricity load in smart grids, as evidenced by the lowest mean absolute error (39.27), root mean squared error (29.13), and mean absolute percentage error (2.84).