Green certificate trading was introduced by the Electricity Act 2000. Electricity suppliers based in Austria have to include 8% of electricity generated by domestic small-scale hydropower plants in the energy sold to final customers. Final customers purchasing electricity directly from foreign suppliers are required to prove that 8% of the electricity they consume is generated by domestic small-scale hydropower plants. ?Small-scale hydropower certificates? are used as proof. Hydropower plants with a maximum capacity of up to 10 MW are designated by the provincial government, entitling their operators to issue such certificates. The designations are notified to Electrizitats-Control GmbH. Small-scale hydropower certificates are in units of 100 kWh. They have to be authenticated by the grid operator of the respective plant. The system is electronic and is monitored by Elektrizitats- Control GmbH. Certificates can be banked for up to two years. In the case of non-compliance, an equalisation levy is imposed upon electricity suppliers and final customers by the provinces.