In this graduate thesis, the working principle of thermoelectric generator, ie thermoelectric module, has been explained. An insight into the physical basis of the principle was given and Seebeck's, Peltier's and Thomson's effects were explained, which enable the generation of electricity by the temperature gradient on a thermoelectric module. Further insight into the history of the development of thermoelectric modules and insight into the materials used to build them are given. The influence of temperature mismatch on the generated power of thermoelectric modules that are electrically connected in series or in parallel has been explained. After the theoretical background, a thermoelectric module was tested, based on which a thermoelectric generator (TEG) was calculated and made for low power consumption. After the preparation the TEG was tested and the results obtained were compared with the calculations. It can be concluded that TEGs are not very much applied in practice due to their technical constraints (low efficiency, relatively high price, high internal resistance) but that the use of newer technologies, in particular the higher quality materials, will significantly increase their use in the future.