The public lighting systems sector is at the beginning of important technological changes, due to economic and environmental sustainability reasons. It is quite easy to operate, thanks to a considerable installation uniformity. It is therefore programmable and the public decision makers have to make choices involving energy and maintenance savings, environmental sustainability, public security and safety, aesthetic improvement of the cities, relationships with citizens. The main technical matters are the light sources (efficient lamps and modern LEDs) and automatic light control systems. The implementation can be retro-fitted on the existing installations. It is easy to reach the necessary compromise between the conservation requirements of historical urban sections and the sustainable development. The main purpose of this kind of enterprises is the complete requalification of the whole city lighting plants, or of a large amount of them such as the historical sections. The financial instruments are promoted from the Directive 2006/32/EC on energy end-use efficiency and energy services, using private capitals (Energy Service Companies - ESCo).