Following the reform of energy sectors, some countries have used engineering norm models in incentive regulation of network utilities. In 2003, Sweden adopted this approach to regulation of electricity distribution networks. This paper examines whether the norm models represent the real networks and create incentives for performance improvement. We analyse data from 138 network concession holders between 2000 and 2007. The results show that norm models are not adequate representations of real networks. Also, utilities that perform better than their norm models tend to behave opportunistically. Finally, we find that private utilities respond more strongly to incentives.