European Union carbon emissions allowances (EUA) price fluctuations can affect electricity companies' stock market values as these oscillations may change firms' profitability and thus investors' decisions. This outcome can differ not only contingent on the EU ETS Phase, but also on firms' generation mix. Moreover, stock markets may react differently to EUA increases in comparison to decreases, thus asymmetrically. By using daily data from January 2008 to July 2014, this article analyses long-run equilibrium relations and short-run interactions between the aggregated electricity industry stock market returns and EUA price changes. Moreover, we test if the relationship between EUA price variations and electricity stock returns is asymmetric and if the carbon price effect and the asymmetry are power firm-specific. Adding to earlier studies, we initially provide an inspection of the individual impact of EU ETS Phase II and on-going Phase III; followed by a comparative analysis between power firms which core activity relies on renewable energy sources and those whose sources are fundamentally non-renewable ones. A statistically significant positive long-run impact of EU ETS on the aggregated power sector stock market return is found concerning Phase II and works asymmetrically. Moreover, evidence is provided demonstrating that asymmetry and EUA effects are power firm-specific. (C) 2016 Elsevier Ltd. All rights reserved.