Regulation cannot always move as fast as innovation. Regulatory experiments enable real-life testing of new products, services or business models by allowing derogations from existing rules while maintaining the protection of energy consumers. The outcomes of these experiments inform future regulation. In this chapter, we discuss experiences with regulatory experimentation in the energy sector of three pioneering countries: the Netherlands, Great Britain and Italy. We compare the implementations along six dimensions: eligible project promoters, scope of the derogations, length of the derogations, administration of the experiments, funding, and transparency. We also describe how the early approaches have evolved in these countries. Finally, we look ahead and discuss how learnings can be applied to enable experimentation at the European level involving technologies that are expected to become important to enable the green transition.