When do technological progress, energy savings, and safety outweigh the harmful effects on human health? Public lighting in Prague is undergoing gradual modernization. Approximately 12% of lamps have so far been equipped with new LED sources, which are designed to reduce energy consumption, increase the feeling of safety, and prepare the infrastructure for future technologies such as smart lighting control or other urban network functions. However, the whiter type of light is causing mixed reactions, as it disrupts the natural alternation of light and darkness to a greater extent. Scientific studies warn that artificial lighting can suppress the biological rhythms of organisms and negatively affect humans, animals, and plants. The discussion will focus on what kind of light we need in the city and how to find a balance between technical efficiency, the quality of the nighttime environment, and responsibility towards residents and nature.