The EU policy aims towards low carbon economy by establishing a goal of reduction of 93-99% in greenhouse gas emissions in energy sector by 2050. This means a complete energy transition from the fossil fuel based systems to mostly renewable and low-carbon based energy systems. In order to integrate variable renewable energy sources, day-ahead and intraday electricity markets influence, demand - response technologies implementation and fossil fuel powered thermal power plants' flexibility considerations need to be analysed. Along with the integration of solar photovoltaics, demand - response technologies (power-to-heat and vehicle-to-grid concepts) needed to balance the system, were deployed. In calculations performed on the case study of Croatia in years 2014 and 2030, a moderate introduction of heat storages in Croatian combined heat and power plants, introduction of electric vehicles and flexible operation of power plants enabled the integration of up to 2000 MW installed capacities of solar photovoltaic plants. The main integration criteria, a cumulative critical excess electricity production from solar and wind power, was kept under 5%. Results of this approach are the reduction in full load hours of economically feasible operation for Croatian power plants up to 2000 and combined heat and power plants to up to 3000. (C) 2019 Elsevier Ltd. All rights reserved.