In network industries the market reform that is being pursued by national and supranational authorities should lead to an improvement of efficiency, which spills over into a beneficial macroeconomic impact. This paper presents two alternative simulations of the potential impact in Belgium. These simulations give very different outcomes, but are still complementary. A macroeconometric approach seems to be more realistic in the short and mid term because it has been built up from observed behavioural relationships. A general-equilibrium approach gives rise to drawing some lessons about the conditions that make the impact more pronounced in the long term.