Modernization of power plants using fossil fuels of Petrašiūnai Power Station in order to adapt them to use renewable energy resources (biofuel) and to produce electricity and thermal energy. Analysis of electricity and heat market, possibilities to sell electricity on the Electricity Exchange or receive investment support, the rate of purchase of electricity were performed and evaluated in the work. Financial-economic calculations after the review of the existing legislation were prepared. Simulation of different operating modes of the power station under construction was also carried out in the work. Recommendations and offers under what conditions it would be purposeful to implement the project in question were provided.