There has been growing interest in the distributed solar generation (DSG) system in accordance with the 'Post-2020 Climate Change Agreement', especially for the reduction of greenhouse gas emissions from buildings. In this respect, this study aimed to develop an integrated model for estimating the techno-economic performance of the DSG system on building fa ades, with a focus on energy demand and supply. The integrated model was developed in five stages: (i) definition of design variables affecting the DSG system on building fa ades; (ii) establishment of a standard database for the DSG system on building fa ades using energy simulation; (iii) technical analysis of the DSG system on building fa ades using the finite element method; (iv) economic analysis of the DSG system on building fa ades through life-cycle cost analysis; and (v) systemization. Detailed analyses were conducted in three aspects: (i) nonlinearity analysis; (ii) validation of the developed model; and (iii) practical application (to the 'S' apartment block in South Korea). With the newly developed integrated model (i-FEM), it was found that the technical performance of the DSG system could be accurately estimated in only 6 s: (i) heating energy demand (1.01%); (ii) cooling energy demand (9.27%); and (iii) building energy supply (3.55%). It is expected that decision-makers (e.g. construction managers or facility managers) can use the newly developed integrated model (i-FEM) to evaluate the potential impact of the DSG system on building facades in a timely and accurate manner.