This paper analyses the role of the managers' non-pecuniary private benefits in an incomplete contract approach to the regulation of utilities. Private benefits may take various forms: excessive job security, perks, overstaffing, feeling of power. The model describes the relationship between a government and the manager of a firm which produces a pure public good, under private or public ownership. The firm's production is characterized by its quantity and its flexibility, the latter corresponding to adaptability to changes in consumers' tastes or to new technologies. A larger output quantity entails larger private benefits to the manager, while increasing flexibility runs counter to the managers' private benefits. The manager decides upon non-verifiable investment in human and non-human capital so as to facilitate an increase in the output quantity (capacity investment) or to improve the firm's flexibility (investment in organizational adaptability). We compare the effects of the ownership regime on the manager's incentives to invest and on the aggregate welfare. The private firm under-invests in capacity and organizational flexibility. This is because the government holds up a part of the gains through ex post renegotiation of the initial (incomplete) contract. Our analysis also highlights a fundamental bias in the investment behavior of the state-owned firm: the manager of the public firm only invests in capacity (he may even invest more than under private ownership) but he never invests in organizational adaptability. The model shows that an increase in the government's bargaining power exacerbates the hold up problem when the firm is privately owned, but that this result may be reversed for capacity investment under public ownership. Finally, we show that the superiority of private or public ownership depends simultaneously on three factors: the respective bargaining power of the manager and of the government, the degree of specificity of investments and the relative weight of quantity and flexibility concerns in the social welfare.