While increasing the share of renewable energy to 20% is a challenge for grid stability, working towards a 100% renewable energy supply requires a completely new approach. Small island grids are the ideal platform to start achieving tomorrow's energy concepts today.To develop the necessary technologies for a high level renewable energy island system, Younicos AG built a hardware and software development and test site in Berlin. The actual system testing shows that the ability to switch off the diesel generator -i.e. guarantee a stable grid exclusively using fluctuating sources and batteries and without rotating masses, gives the freedom to choose any renewable energy configuration between 0 and 100%. Consequently, the renewable energy system layout can be set up according to the island's ecological and economical goals.A hybrid system with a high renewable penetration can generate substantial savings by substituting large shares of fuel for electricity generation. Therefore, in addition to the technological solutions, procedures and business models are being developed to identify the economic optimal configuration for isolated systems under a given set of climate and load conditions. The technical approach, results of the test phase and key parameters of a supply system based on renewables and storage will be summarized in this paper.