This study, conducted by a team from various countries and supported by the International Energy Agency (IEA) and its Technology Collaboration Programme, aims to evaluate the capabilities of eight existing simulation tools for Building Integrated Photovoltaics (BIPV) energy simulation. The research focuses on a single building project with three different types of BIPV installations, assessing the tools' performance in modeling building geometry, selecting weather data, setting system layouts, evaluating solar resources, estimating energy losses, and assessing energy generation. Key findings include: - The selection of weather and solar resource data significantly impacts energy forecasting. - Some PV simulation tools operate as "black boxes," accepting only specific data formats like TMY or GHI, while others are more versatile, accepting multiple years of data and different solar irradiance components. - Simplifications were necessary to find common ground between the tools, leading to the exclusive use of TMY weather data for simulation and comparison with one year's measured yield. The study highlights the importance of flexible and versatile tools in BIPV energy simulation to ensure accurate and reliable energy forecasting.This study, conducted by a team from various countries and supported by the International Energy Agency (IEA) and its Technology Collaboration Programme, aims to evaluate the capabilities of eight existing simulation tools for Building Integrated Photovoltaics (BIPV) energy simulation. The research focuses on a single building project with three different types of BIPV installations, assessing the tools' performance in modeling building geometry, selecting weather data, setting system layouts, evaluating solar resources, estimating energy losses, and assessing energy generation. Key findings include: - The selection of weather and solar resource data significantly impacts energy forecasting. - Some PV simulation tools operate as "black boxes," accepting only specific data formats like TMY or GHI, while others are more versatile, accepting multiple years of data and different solar irradiance components. - Simplifications were necessary to find common ground between the tools, leading to the exclusive use of TMY weather data for simulation and comparison with one year's measured yield. The study highlights the importance of flexible and versatile tools in BIPV energy simulation to ensure accurate and reliable energy forecasting.