The record of the past 40 years shows that in the nation's system for generating, transmitting, and distributing electricity, some blackouts are inevitable. Natural hazards produce many local and regional blackouts (Table 14.1), and society has learned to cope with them. Power outages occur more frequently than theory predicts, however, and despite years of promises and technology development, the frequency of large blackouts has not decreased over time (Figure 14.1). Making cost-effective improvements in control and operation of the grid is important; however, data suggest that reducing the frequency of these low-probability, high-consequence events will become increasingly expensive.

The U.S. and Canada blackout on August 14, 2003, revealed that many private institutions are far ahead of the public sector in defining their critical missions and taking steps to protect them when the lights go out. During the one-day blackout, some hospitals and television stations in New York City, Toronto, Cleveland, and Detroit were able to stay open because they had backup generators. Services in other sectors, however, could not be delivered. Elevators in office buildings were stuck between floors, trains stopped between stations, traffic signals went dark, cell phones lost reception, and, in Cleveland, water ceased to flow and sewers overflowed when the electric-powered pumps stopped functioning. If the blackout had persisted for longer than a day, the region's public health and welfare would have begun to suffer from the failures of more and more socially critical missions (see Appendix 14.A for the effects of blackouts on an array of critical services).