The introduction of emissions trading and the design of allocation plans have far-reaching implications on the development of the power plant mix, the CO₂-emissions, and the power plant investments of energy utilities. Especially CO₂- and electricity prices as well as the design of the allocation rules get more and more important for investment strategies of energy utilities. For this reason it is necessary to analyse the impacts of the Emission Trading Scheme on the future of power generation and investment decisions in power industry. For this purpose this paper shows some possibilities to analyse the impact of different allocation methods by using optimizing energy system models. Results show that the emission allocation scheme has a significant influence on power generation planning and power plant investments and with this on the evolution of CO₂-emission and electricity market.