In this research, an analytical method for quantification of the thermal energy performance improvement for a building integrated photovoltaic double-skin façade has provided. The system has been suggested as a retrofit measure for an existing building in Tehran. The effect of thermal performance has been analyzed through computer-assisted developed code using engineering equation solver software. Three scenarios have been defined and for each scenario temperature and velocity profiles have provided through continuity, momentum and energy equations. As the monocrystalline photovoltaic modules and the double-glazed windows are more conventional in the current condition in Tehran, the authors have considered them for the analysis. A comparison of results for this study is valuable for the cases intending to select between the glass and the photovoltaic as the outer façade. The quantitative results illustrate that the proposed system would be able to reduce the cooling demand in the summer case by 18.5 kilowatts, which is around 8.7 percent of the current cooling load. According to the results of the sensitivity analysis, both glass and photovoltaic façades have a greater impact in terms of energy saving in the summer case. According to the results of the analysis, by increasing the ratio between the photovoltaic outer façade to the surface area of the glass section, the amount of the energy saving due to the total cooling load reduction will increase. The results of the analysis showed that the application of the suggested system will reduce the thermal load by 2.1 percent in the winter season.