Benchmark studies of the environmental impacts of buildings often overlook the contribution of lighting systems. This omission presents a significant knowledge gap, especially given the growing focus on energy-efficient technologies and sustainable building designs. To address this gap, the life cycle assessment method was used to calculate the environmental impacts of lighting systems, focusing on the Global Warming Potential (GWP) indicator. An in-depth review of databases and programs across the 27 European Union member states was also conducted. The study analyzed both the absolute and relative contributions of lighting systems to the overall environmental impacts of buildings, with a specific focus on the situation in Denmark. A total of 101 Environmental Product Declarations (EPDs) covering 753 LED lighting products were identified. Material-related impacts accounted for 1–12% of the total GWP, while energy used during operations contributed 6–24%. These results emphasize the importance of both embodied and operational impacts. Improving the luminous efficacy of lighting systems emerges as a more effective and feasible strategy to reduce a building’s GWP than lowering overall energy use or grid carbon intensity. In countries with high-carbon electricity, reducing the operational impacts is critical. Elsewhere, selecting lighting systems with low embodied impacts is also essential.