Foreign investment and international assistance could be a potential source of “greening” effects, both directly through transfers of more energy-efficient and environment-friendly technologies and indirectly by facilitating spillovers to domestic firms through best practices in environment-friendly productions, technologies and management (Section 4). These export-oriented sectors have also attracted an important share of FDI (20% of the FDI stock). By ensuring transit of natural gas from Russia to Europe, Ukraine also plays a strategic role in international energy relations. Its total primary energy supply (TPES) is dominated by four energy resources: natural gas represents 41%, followed by coal (29%), nuclear energy (18%) and oil (11%). Electricity production comes mainly from nuclear power plants (48%), followed by coal power generation (34%) (Figure 4.1). Heating depends almost exclusively on gas.