Industrial heritage is a witness of a civilizational breakthrough, which was so important that we call it a revolution. The architectural heritage of power plant buildings manifests a transition to the Age of Electricity. Power plants as a new typological type were challenging for engineers and architects, who tried to create a symbiosis between the highest technological realization and the aesthetics of its architecture. The result is a wide variety of architectural expressions of power plant buildings. Nevertheless, the results of previous generations' industrial production are largely overlooked and underestimated in Slovakia. The architecture of industrial heritage, as a relatively young structural layer, is vulnerable and endangered. The heritage of power plants is very rich, but yet undiscovered. So far its architecture has received very little attention, thus its meaning is seemingly underestimated. The research of this thesis is therefore focused on mapping the primary buildings of power plants in Slovakia and on on identifying their architectural characteristics. The part of this work consists of the inventorisation and chronologisation of power plants, resulting in a tabular database containing basic information about the buildings. This work is putting the buildings into the historical context and describing their constructional development. The other part of the thesis represents detailed documentation of chosen plants through archival and on-site research. The results are listed in a specially conceived documentation cards. Architectural characteristics' identification was performed by a synthetically acquired knowledge and a comparison of the individual power plant buildings. The selected preserved power plants were proposed to be registered as national monuments. Proposed sequence of steps was verified by the process of this research. Sequence of steps has been incorporated into the methodology of documentation of power plants. Systematical documentation of power plants was developed for the needs of this thesis.