In international co-operations dissemination strategies for renewable energy systems are analysed and economic evaluations are conducted considering external costs of various renewable energy carriers. The EEG co-operates within the IEA programmes on "Photovoltaic Power Systems" and "Solar Heating and Cooling". The major technologies investigated are: Wind, PV, Solar-thermal systems and biomass applications. Furthermore, emphasis is put on the derivation of efficient promotion strategies and an evaluation of financial incentives as a dissemination tool. Another objective is to investigate optimal portfolios considering various types of renewables to meet renewable portfolio standards. Currently, this is a very important issue because of both, a new Austrian electricity market organisation law (requiring 4% new renewables by 2007) and the Austrian commitment to reduce greenhouse gas emissions by 13% within the EU-Bubble. Finally, another important focus is to analyse the value of various types of renewables from social point-of-view.