By stipulating a light loss factor when planning the lighting, the intervals at which maintenance is to be carried out can be controlled. By keeping light loss factors low, the lighting level will initially be higher and the period during which luminous flux is gradually reduced to below the critical value will be extended. Using a suitable maintenance factor, lamp replacement and the cleaning of luminaires can be timed to take place simultaneously. The adjustment of luminaires is also classified as maintenance in the interest of the qualitative aspects of the lighting installation. In the area of display lighting in particular, luminaires have to be realigned to accommodate the layout of a new arrangement. A maintenance plan should enable the operator to service the installation at regular intervals, checking whether the technical requirements are being met and the lighting is performing as planned.