The nucleus of today's Elektroprojekt was formed in 1945 when Elektrotehničko poduzeće Hrvatske, ELPOH (Croatian Electrical Engineering Company) was established. In 1946, a hydroelectric power plant design group left ELPOH to join Hidroelektra, a new company established to design and build hydroelectric power plants. In January 1948, when Inženjerski projektni zavod, IPD (Engineering Design Institute) was founded, Hidroelektra’s design engineers joined IPD in which they formed its Hydroelectric Power Plants Department with 16 employees of which 9 engineers. On 12 March 1949, the Government of the Federal People's Republic of Yugoslavia established Hidroelektroprojekt, a company for engineering design of hydroelectric power plants and field investigations with branch offices in all capitals of the then republics except Montenegro. On 1 November 1949, the hydroelectric power plants design group left IPZ for Hidroelektroprojekt Zagreb where it was engaged on hydroelectric power plants design and monitoring at the territory of the People's Republic of Croatia. This was the date when the new company actually became independent, although its first employee was entered into the Hidroelektroprojekt registry and started working in the company already on 1 April 1949. Based on these facts, 1 April 1949 is considered the Elektroprojekt establishment date.
On 8 April 1951, Hidroelektroprojekt was joined by Termoelektroprojekt and a substations design group so the business operations programme expanded to design of all power generation plants and facilities. After the responsibility in this sector was passed from the federal to the republic administration level, the name of the company was changed by the decision the Government of the People's Republic of Croatia to Elektroprojekt – company for design of power generation facilities.
Since 1949, Elektroprojekt has grown into a strong consulting engineers organisation inseparably linked to the development of power generation and water sectors, particularly in Croatia. Until 1953, Elektroprojekt operations – engineering design of hydroelectric power plants, thermal power plants, substations, conducting of field investigations and preparation of studies - were limited to the domestic market. In 1954, Elektroprojekt took its first steps abroad. Its engagement on the Zawgyi Hydroelectric Power Plant in Burma was the start of Elektroprojekt continuous but varying international presence. Since 28 January 1955 the company has been registered for foreign trade and implementation of international capital projects. Elektroprojekt has since rendered an array of services abroad, particularly in developing countries (Burma, Ethiopia, Egypt, Iran, Libya, Algeria, India), but also in Greece, Spain and the USA.
The results of work of Elektroprojekt experts constitute a unique archive of more than 23,000 design volumes, including design documentation for the majority of hydroelectric power plants and thermal power plants and other facilities built in the Republic of Croatia. Since its establishment, Elektroprojekt has maintained its core business and expanded its field of activities based on the circumstances and requirements of the economic development and market demands. Thus, in addition to water resources management, environmental and nature protection, the scope of Elektroprojekt activities expanded to include the utilization of renewable energy sources, such as wind and solar energy, biomass and geothermal energy, and to infrastructure projects such as tram rails and cable cars.