Carbon fibre reinforced polymer (CFRP) is increasingly used for aero-structure applications due to their high strength-to-weight ratio. The integration of the on-board electrical power system (EPS) with CFRP is challenging due to the requirement to thermally and electrically isolate these systems to meet existing safety standards. By capturing the thermal characteristics of CFRP at a macro (component) scale for CFRP components, it is possible to understand, and design for, the increased integration of the EPS into CFRP aero-components. A significant challenge is to develop a macroscale characterisation of CFRP which is not only of an appropriate fidelity for compatibility with systems level models of an EPS, but can be used to represent different geometries of CFRP components. This paper presents a novel methodology for capturing a transient, macro-scale thermal characterisation of CFRP with regards to component lay-up and geometry (thickness). The methodology uses experimentally derived thermal responses of specific resin and ply orientation CFRP samples to create generalised relationship for the prediction of thermal transfer in other sample thicknesses of same material type. This methodology can be used to characterise thermal gradients across CFRP components in aircraft EPS integration applications, ultimately informing the optimised integration of the EPS with CFRP.