This study proposes an environmental identity economics theory that can improve our understanding of pro-environmental behaviour. We test the potential of the theory by analysing farmers’ decisions to invest in renewable energy production using a hybrid choice model. Our findings illustrate that farmers with a strong environmental identity require less financial incentive to invest. Furthermore, lower compensation is found to be sufficient to induce farmers with a strong environmental identity to commit to more binding investment contracts. Our findings stress the need for differentiated designs of agri-environmental programmes and mechanisms that enhance farmers’ environmental identity.