Energy geostructures (EG) are an innovative technology in the sustainable energy agenda that can be used to satisfy the heating and cooling needs of the built environment. EGs include several types of geostructures such as piles, walls, tunnels, shafts, sewers. The application of this technology to infrastructure projects is particularly interesting because of the important thermal potential offered by the large surfaces that can be thermally-activated. This study deals with thermo-active walls (Energy walls, EW), which are retaining structures used to sustain the sides of excavations. Aspects related to the hydro-thermal interactions and to the thermal design are here presented. Finally, the testing setup for the execution of a thermal response test on a recently-built EW in western Switzerland is discussed.