The energy use for lighting represents relevant part in the energy balance of office buildings. For this reason, the correct evaluation of the indoor daylight availability, strictly linked to the weather conditions of the site, is a crucial factor to predict the electric use for lighting with more accuracy than the current relevant standard, implemented in the framework of the EPBD. This study compares the indoor daylight levels in an office building, and the related energy performance, calculated according to the relevant standard EN15193-1:2017 and to dynamic climate-based simulation, based on hourly weather data, and those derived by Italian solar radiation dataset. In the latter cases, the electric lighting systems is controlled and switched on/off considering the contribution of daylighting to achieve the visual task set-point. This approach leads to a more realistic evaluation of the daylight autonomy (DA) and, consequently, of the electric lighting demand. In addition to this performance gap assessment, since different operating hours lead to different internal gains, the impact on the space heating and cooling performance of the building is evaluated as well. The simulations, carried out using the EnergyPlus calculation tool, highlighted significant discrepancies in terms of annual energy consumption for lighting (62–78%) and overall energy need. Findings of the study aims at introducing elements of climate-based assessment for a more accurate evaluation of environmental and energy performance and stimulate the upgrade of current standardized approaches, which may lead to relevant performance gap.