Renewable energy sources have eventually become socially accepted, but nowadays the main challenges of this kind of technology production are in the energy market adjustment. Initially, to promote renewable energy sources, the main idea was based on additional funding (incentive) of such sources and to isolate them from the state of energy market. However, renewable energy must participate on energy market in accordance with prices of conventional energy sources as a result of the increasing development of renewable energy technology as well as the intention to achieve a competitive and stable market. This is achieved by changing incentive policies at a national level. The main intent is to implement the feed-in premium (FIP) or quota system (green certifications) in the incentive system. Implementing either system will reduce the cost of all market participants and end-user customers. There are various applications of those models which can be seen in Germany, United Kingdom and in other member states of the European union. A new law has been introduced in the Republic of Croatia representing a new incentive model, transitioning from the feed-in tariff (FIT) to the feed-in premium (FIP). Such a transition is a new challenge for individual investors due to the increase of revenue unpredictability. Setting a plant model in such an environment, using a program like Crystal Ball, can greatly facilitate the strategic planning of renewable energy source investors.