Trombe walls are façade elements which aim is to reduce the heating consumption in buildings. This paper presents the approximate energy savings potential that can be obtained with the use of Trombe walls in Mediterranean climates and some basic design guidelines that should be followed to maximize the energy performance of this device. In this article are shown the results obtained from a parametric study conducted to establish the influence of the main design variables in the energy performance of Trombe walls, and some guidelines for a correct design of this element from an energy point of view.