Privatization, internal market, interconnections, greenhouse gas emission reductions, renewable energy targets… is it possible to reconcile these themes? And if so, will our lights stay on? This is a major concern of a number of players in the energy field, especially the Secretary of State for Energy since he is responsible for guaranteeing the security of supply. In times of increased electricity production by variable energy sources and of distorted investment signals, guaranteeing security of supply is not evident, since the absence of investments in sufficient reserve capacity and – worst case scenario – inadequacy of generation capacity may lead to soaring societal costs. This Working Paper focuses on the specific event that, in spite of all initiatives and mechanisms in place, things go wrong: a national black-out paralyzing the entire Belgian economy for 1 hour and its price tag are analysed.