**Martin Lieskovský 1, Marek Trenˇciansky 1, Andrea Majlingová 2,\* and Július Jankovský <sup>3</sup>**


Received: 1 March 2019; Accepted: 30 April 2019; Published: 6 May 2019

**Abstract:** According to the current circumstances that are related to the effectiveness of the tightened European Union (EU) environmental legislation, which sets minimum requirements for the heat and power sources of energy that are part of the Slovak Electricity System (SES) source mix, an article was prepared to summarize the information regarding energy and environmental legislation, which is in force as in the EU as in Slovakia. This information was completed with a description on the current situation and requirements for the safety and reliability of the "new" mix of sources and technologies of electricity production within the SES in terms of energy and economic efficiency and environmental consequences.

**Keywords:** energy resource; energy security; energy sources; Slovakia
