Finland is committed to aim for a carbon-neutral energy system by 2023. The transition is in progress with increasing shares of various forms of low-carbon production and significant reductions in the share of energy production from coal and natural gas, for example. Finland has traditionally been strong in the use of renewable energy thanks to wood-based fuels availability. However, a significant part of the energy is still produced from fossil fuels in Finland. The energy system has been in constant evolution throughout history. Recently, climate change mitigation has made carbon neutrality the single biggest goal in energy system development, which has a major impact on current decision-making. In addition to carbon neutrality, the change must consider two other particularly important and ongoing societal objectives such as security of supply and service of the energy system, and cost-effectiveness. The future energy system will be affected by many expectations and parallel developments. These include the arrival of new energy sources on the market and their integration into the system, the progress of electrification, the development of energy technologies and changes in cost-efficiency, the growing importance of energy storage, the carbon capture development, and plans for the hydrogen economy. There are numerous possible directions for development, and they are not mutually exclusive. However, it creates science-based, urgent information needs and challenges for energy system decision-making. As decisions have to be taken that simultaneously create the conditions for the achievement of several objectives, partly cross-impacting each other. This report offers a clear and comprehensive overview of energy system status in Finland including the main trends. The report provides basic general information of the different types of energy production, energy storage, energy efficiency and savings as well as the entire energy system, including system integration. In addition, the aim is to present basic information of the different types of energy production, the current state of the energy system and future trends. The report is intended for all those who are interested in the trends in the energy system and aims to present relatively complex entities in an understandable way and to provide an overview of the factors involved in the development of the energy system. The report has been written by 19 experts in their field from the Faculty of Energy Systems at LUT University. The report starts with a summary of the views of public organisations on future trends and scenarios for energy systems. The most relevant of these are the views and scenario calculations of the Intergovernmental Panel on Climate Change (IPCC), the EU, the Nordic Council of Ministers' organisation called Nordic Energy Research (NER) and the Finnish Climate and Energy Strategy. The views contain the same basic elements related to energy systems and also partly contain many different future scenarios. For example, the evaluation models reviewed by the IPCC include more than 2 500 scenarios. The report presents basic information on the technologies and characteristics of all the main energy production methods in Finland, considering the sustainability of the production method and the different needs of society. In addition, reports covers topics such as energy system integration costs, hydrogen economy, carbon capture and utilisation, energy storage and carriers, energy efficiency, energy savings and consumption flexibility. The intention is to provide the reader as comprehensive a basic understanding as possible of the main technologies of the energy system and the most important elements of its development. Besides presenting the different forms of energy production and the main technologies, the report also considers the energy system as a whole and the various priorities for the future. The current state of the energy system is examined in particular for electricity and heat and also briefly for industry and transport. The report also is discussed the significance and role of the three main energy sources in the development of the national energy system. In Finland, the main energy sources for the energy system development are variable renewable energy, nuclear power and biomass. In addition, the report provides information on important elements of system integration, such as sector integration, system infrastructure, the functioning of the energy market and system-level investments, and export opportunities related to carbon neutrality expertise in Finland. The main issues of the energy system development are currently related to variable renewable energy, especially wind power in Finland. It plays an important role in transforming energy consumption in many sectors towards carbon neutrality and will grow significantly in the coming years. As the wind dependent and variable production share increases, ensuring operational reliability will require significant structural changes and system development to maintain a balance between production and consumption under all conditions. The main tools to achieve these purposes include energy storage in different time periods, weather-independent and controllable forms of energy production, power reserves, consumption flexibility and integration between different sectors. This report aims to provide the basic information needed to understand the whole picture and its various components. Publishers version