This paper investigates the applicability of currently available analytical, empirical and numerical heat flow models for interpreting thermal response tests (TRT) of quadratic cross section precast pile heat exchangers. A 3D finite element model (FEM) is utilised for interpreting five TRTs by inverse modelling. The calibrated estimates of soil and concrete thermal conductivity are consistent with independent laboratory measurements. Due to the computational cost of inverting the 3D model, simpler models are utilised in additional calibrations. Interpretations based on semi-empirical pile G-functions yield soil thermal conductivity estimates statistically similar to those obtained from the 3D FEM inverse modelling, given minimum testing times of 60 h. Reliable estimates of pile thermal resistance can only be obtained from type curves computed with 3D FEM models. This study highlights the potential of applying TRTs for sizing quadratic, precast pile heat exchanger foundations. •TRTs on precast quadratic energy piles are interpreted using 3D numerical analysis.•Thermal conductivity from inverse analysis closely matches laboratory test results.•Simpler models without concrete capacity or pile length are inappropriate.•Semi-empirical G-functions give acceptable thermal conductivity but not resistance.•Minimum recommended TRT duration for 30 cm square piles is 60 h.