The concept of energy efficiency is closely related to the concept of energy and can be considered in different sectors of the economy of a country. Because of the importance of the tourism sector for the development of the Croatian economy, it is necessary to explore the possibility of reducing costs that can be achieved through increased energy efficiency and, therefore, this work contributes to this underexplored area. The subject of this final work is to analyze the energy efficiency in selected Mediterranean countries (Croatia, Slovenia, Greece, Italy and Turkey) on a sample of 51 companies of nautical tourism. Given that energy efficiency is closely related to renewable energy sources, the paper analyzes the impacts of increasing energy efficiency in nautical tourism through greater exploitation of solar energy, i.e. trough the installation of photovoltaic modules on vessels. One of the reasons for poor utilization of renewable energy sources in the Republic of Croatia is still a high rate of exploitation of this type of energy sources. Their implementation depends primarily on administrative support and stimulus measures. However, the price does not include the utilization and cost of environmental protection and the Republic of Croatia should develop economic, legislative, administrative, technical and organizational system and adequate measures in order for renewables sources to have a multiplier effect on the overall economy. Based on the obtained and processed data collected during the survey that was completed by 51 company in five selected Mediterranean countries it is possible to conclude that there is great potential for more intensive use of renewable energy sources in nautical tourism. The potential lies in the use of photovoltaic modules to collect solar energy on vessels and reducing the use of fossil fuels. Research has shown that there are many obstacles in achieving higher levels of energy efficiency, mostly in complicated procedures and lack of financial resources including the lack of information. The key to success, according to the research results, lies in the systematic inclusion of small businesses in the process of informing about the possibilities of financing and the availability of financial resources, in removing the complicated procedures and excessive administration. Interest of subjects for the implementation of various educational measures exist and there has been noticed a low level of awareness about the possibilities and measures for improving energy efficiency. Financial analysis of a hypothetical project of installation of photovoltaic modules on the vessels of nautical tourism has shown that the project is cost-effective by analyzing the economic and financial indicators of the project with associated criteria. All the economic and financial indicators of the project are positive including the net cash flow of the project that in all the years of effectuation remains positive and sufficient to return the loan. Time of return occurs in the second year of the project while even unfavorable input changes will not affect positive financial indicators of the project.