The introduction of permanent lighting in caves is a major perturbation of natural conditions and has to be considered in terms of environmental global and /or local impacts.The global impact of a lighting system has to be evaluated in terms of thermal energy emitted in the cave. In the Gargas Cave, an energetic threshold corresponding to the loss of the cave natural regulation is identified. The cave management has to balance the energy brought by visitors and the energy of the lighting installation. An efficient lighting system would release less thermal energy and more visitors could be allowed. Even if the whole lightening system has negligible global effect on the cave, local impacts around each lamp may cause irreversible degradation of speleothems or rock paintings. Experimental thermal data in the Moulis Cave show that lighting can induce changes in air /rock interface exchanges due to exceeding energy absorbed by rock. Owing to these experiments, we are entitled to propose different levels of risk.