*3.1. Data Sources*

The study was focused on European Union households. The research material was from Eurostat "Energy balance sheets" [7].

The energy balance is the most complete statistical data of energy products and their flow in the economy. The energy balance offers a complete view on the energy situation of a country and of individual sectors (e.g., households). The energy balance is a multi-purpose tool, is the natural starting point to study the energy sector [70].

The research entities were the countries of the European Union. The subject of the research were various sources of renewable energy used by households, i.e.,




The data for the different products are expressed in a common energy unit: thousands of tons of oil equivalent (ktoe) [70].
