A Thermoelectric Cooling-Heating Unit (TCHU) is an innovative technology that uses the thermoelectric phenomena as a heating-cooling system for buildings. In TCHU, a direct current (DC) electrical current supplies the power to a Thermoelectric Equipment (TE) heat-pump system, which can transfer heat in one direction or another depending on the current flow. The unit is integrated in the building envelope. At this stage of the study, a second prototype of TCHU has been developed using commercially available TE technologies. In this case, a vertical configuration of 16 TE modules is studied for their potential application as a heating and cooling system for residential buildings. Different nocturnal tests have been developed to evaluate the performance of the new system under real conditions and to determine the coefficient of performance for these TE modules when operating under different voltage regimes. It has been studied not only the cooling mode but also the heating mode. Based on the measured data, it has been demonstrated that the system can be successfully installed as a heating or cooling system in buildings. Tests have confirmed the huge relevance of the temperature difference between the two sides of the cells, taking especial relevance in the cooling mode. It has also been demonstrated that for the cooling mode it is better to work with low voltage values. Besides, some theoretical analyses have been developed in order to find out the most suitable configuration to obtain the best Coefficient of Performance (COP) of the unit in both cooling and heating. (C) 2017 Elsevier Ltd. All rights reserved.