Key concepts like waste heat recycling or waste heat recovery are the basic ideas in thermoelectricity so as to the design the newest solid state sources of energy for a stable supply of electricity and environmental protection. According to several theoretical predictions; at device level, the geometry and configuration of the thermoelectric legs are crucial in the thermoelectric performance of the thermoelectric modules. Unlike to conventional geometry thermoelectric legs, asymmetrical (pyramidal) legs could help by lowering the overall thermal conductance of the device so as to increase the temperature gradient in the legs, as well as by harnessing the Thomson effect, which is generally neglected in conventional symmetrical (rectangular) thermoelectric legs. Curiously, experimental studies confirming the previous predictions have not been carried out so far, perhaps because of the existing constraints to fabricate thermoelectric legs with complex geometrical shapes. In this work, based on the promising enhancement of the thermoelectric performance in thermoelectric modules via legs with non-constant cross sections, it has been developed a novel design of a thermoelectric module having asymmetrical legs with truncated square pyramid shape, and by first time it has been validated experimentally its thermoelectric performance by realizing a proof-of concept device which shows to have almost twofold the thermoelectric figure of merit as compared to conventional one with a constant square cross section. Besides, the variables required to engineer enhanced performance thermoelectric devices are properly identified for use as power sources especially in low consumption portable devices. Therefore, the present results prove that geometrical configuration of the device legs can improve significantly the thermoelectric performance of the device. (C) 2017 Elsevier Ltd. All rights reserved.