Energy cooperatives are witnessing substantial growth across the European Union. However, despite the desire to be inclusive and to foster diversity, the representation of women in energy cooperatives is still limited. The study aimed to verify the strength of the endorsement of gender stereotypes within energy cooperatives and, in the case of women, the factors stereotypes are associated to. Data were collected in two cooperatives, ènostra in Italy and Ecopower in Belgium, for a total of 5690 respondents. Apart from being among the most important cooperatives in their respective countries, the two represent an interesting comparative case because in ènostra women and men are almost equally represented and the president is a woman, while in Ecopower women are underrepresented and the board of directors is male-dominated. For both cooperatives, the results suggested that women had lower self-assessment of knowledge about energy than men and that they recognised, more so than men, the importance of the presence of women on the board of directors (BoD). Finally, we found that women with stronger gender stereotypes about energy exhibited lower self-assessment of knowledge but a greater tendency to increase it after joining the cooperative and they attributed slightly more importance to the presence of women on the cooperative BoD.