Pile Heat Exchangers (PHE) are an attractive solution to reduce both costs and greenhouse gas emissions for new buildings. However, most state-or-the-art PHE thermal models overlook the heat capacitance of the pile concrete, which is known to be important in thermal analysis. A semi-analytical (SA) model accounting for the pile concrete inertia is developed and validated against a finite-element code. Analysis shows that accounting for PHE inertia always leads to higher performances compared to purely resistive models. Application of the model to interpretation of thermal response tests data allows estimates to be made of the minimum duration test required to obtain reliable values of ground and concrete conductivities. (C) 2019 Elsevier Ltd. All rights reserved.