Grid tariffs are the main source of income for distribution system operators (DSOs). Reductions of tariffs increase the cost pressure on DSOs; assuming they work efficiently, tariff reductions potentially lead to a decrease of the electricity system's quality if no reliability of supply criteria are incorporated in the regulatory system. Our statistical analysis shows that the correlation between grid tariffs and electricity supply interruptions in a regulatory regime neglecting this incorporation is significant and that furthermore decreasing tariffs harm the reliability of supply even in the short run. Our econometric analysis of the influence of tariffs on reliability of supply shows a significant correlation between the grid tariffs and the duration of power outages in the Austrian electricity grid; an annual average interruption duration per installed capacity of a specific grid increases ceteris paribus by 1.36 min if the grid tariff of this specific grid is decreased in the previous year by 1(sic)/MWh. (C) 2008 Elsevier Ltd. All rights reserved.