## 3 Results
### Modeling Results for 24 BIPV Projects  
Tables 2-4 present results for 24 selected BIPV projects, focusing on the findings of the energy and financial modelling and the design features. The quantitative modelling results for each case could be consulted from those tables. To provide an overview for each type of building, Figures 4-6 summarize the annual energy production per nominal capacity installed, self-sufficiency and self-consumption, return on investment (ROI) and capital expenditure (CAPEX), respectively.  
Residential projects were mostly designed to be energy-plus buildings or NZEB. They have the highest kWh/kWp.year in some cases, as the roof/facade proportion was the highest. There were also relatively low values due to shading, which resulted in a similar performance with office buildings regarding the mean value (Figure 4). Although PV systems were often modelled on the highest irradiation spot (south roof and facade for ex.), the building's height also limits precautions against shading. The initial investments (as the nominal capacity) were low, as residential buildings were restrained to 10-15 kWp, mostly by the net metering limits. The fastest ROI was found to be 6.1 years (building 6, Table 2), in Spain, thanks to a combination of the feed-in tariff and exceptional irradiation (as well as highest yield per kWp). Self-sufficiency ratios were high for residential buildings (even more than %100), yet the self-consumption ratios were difficult to achieve (6-50%). The self-consumption could be improved thanks to a 6 kWh battery, from 50% to 75%, according to the modelling in DEMKIT software. The battery also reduced the original ROI of 20% for the case inspected.  
Figure 3: Average irradiance over the group of buildings (**a**), transparent BIPV windows (**b**) wiring of the BIPV cells and modules (**c**).  
Figure 4: Annual BIPV production per photovoltaic (PV) nominal capacity installed for three types of buildings.  
Figure 5: Self-Consumption (**a**) and self-sufficiency (**b**) ratios in percentages for three types of buildings.  
Figure 6: Return of investment (**a**) and capital expenditure (**b**) for three types of buildings.  
Regarding office buildings, Table 3 and the figures show a similar payback time for offices as for residential buildings. High self-sufficiency ratios (+95%) compensate for the lower feed-in tariffs. Due to a greater coverage area, or special subventions, the building and energy costs could make office buildings attractive for investors. Almost all office modellings had a payback time under 14 years, except for two (building 3 and 12), due to high installation cost assumptions. However, the desired self-sufficiency levels are hard to reach as the demands for office buildings are high. More transparent BIPVs were used during those projects to respect design requirements.  
Historical buildings were the most diverse, as they included various building types (historical, landmarks, or other). The self-sufficiency and self-consumption ratios varied significantly depending on both the building's and BIPV installation's size. For these buildings, examples were predominantly taken from London, Sydney, Amsterdam, and Rotterdam--big cities and iconic places--except for two buildings, Enschede and Hong-Kong. The CAPEX is closely related to special module requirements and the project size. In general, the historical or iconic buildings and stadiums had larger surfaces than other types of buildings. It should be noted that the installation costs were difficult to estimate due to the special requirements of the building element. Therefore, the initial costs and payback times were slightly higher--between 10 and 18 years--except for buildings 17 and building 23, which used more transparent panels and dealt with many functional, and thereby appearance, aspects; as such, the kWh/kWp.year is significantly less for most of the cases investigated.