Electric Power Systems Research 89 (2012) 191–195 Contents lists available at SciVerse ScienceDirect Electric Power Systems Research jou rn al h om epage: www.elsevier.com/locate/epsr Short communication America’s three electric grids: Are efficiency and reliability functions of grid size? Allan Mazur * , Todd Metcalfe Maxwell School, Syracuse University, 435 Crouse-Hinds Hall, Syracuse, NY 13244, USA a r t i c l e i n f o Article history: Received 18 January 2012 Received in revised form 4 March 2012 Accepted 5 March 2012 Available online 6 April 2012 Keywords: United States grid Efficiency Reliability a b s t r a c t America’s 48 contiguous states (and most of Canada’s population) receive their bulk electricity from three separate electric grids: the huge Eastern Interconnection, the Western Interconnection, and the relatively small Texas grid (often called “ERCOT”). This threefold structure was never centrally planned but grew incrementally, especially during the period 1960–1990. Increasing interconnection has been justified by hopes for improved efficiency and reliability, but it also has downsides, most obviously the risk of widespread blackouts. For recent years, we compare the three grids on efficiency of delivering electricity from generating plants to end users, and on reliability as estimated by monthly customer-hours of power outage (normalized by number of grid customers). Over the period 1990–2010, the Eastern and Western Interconnections had similar efficiencies in trans- mitting and distributing electricity from generators to end users, both persistently better than the Texas grid (ERCOT). Comparisons of reliability were limited to 2007–2010 when outage reporting to the Depart- ment of Energy was apparently more valid than in earlier years. For this recent period, the Western Interconnection was freer of outages than the Eastern or Texas grids. Overall, efficiency and reliability were not linear functions of grid size. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The United States (excluding Alaska and Hawaii) and Canada receive their electricity from four regional grids called the Eastern Interconnection, the Western Interconnection, the Texas Intercon- nection (or ERCOT), and the Quebec Interconnection. Our focus is on the three grids that cover most of the U.S.: East, West and Texas. These were not the result of central planning but grew incremen- tally after World War II, becoming discernible as three separate entities by the 1990s. Past and future integration has been ratio- nalized in part as improving efficiency and reliability. The three U.S. grids differ in size, with the Eastern Interconnec- tion largest and Texas smallest (Table 1). Each is an assemblage of high-voltage transmission lines and lower-voltage distribution lines that connect diverse generating plants (using fossil fuels, nuclear power or hydro and other renewable sources) to numer- ous consumers of electricity (including residential, commercial, industrial and transportation users). The elements of each grid are synchronized to their own 60 Hz alternating current, but are not synchronized with the other two grids. As systems theorists, we find it odd that apparently the three synchronous grids have never been compared as independently functioning entities, to see if one works better than the others. * Corresponding author. Tel.: +1 315 445 1970; fax: +1 315 443 1075. E-mail address: amazur@syr.edu (A. Mazur). The North American Electric Reliability Corporation (NERC) divides the Eastern Interconnection into six reliability regions based on historic associations. Utility companies and transmission organiza- tions focus on their own operations. Such narrow scope gives short shrift to the pieces as components of larger integrated systems. Set against the potential benefits of increased integration are the risk theorists who argue that complex, tightly interconnected systems carry the potential of catastrophic failure, implying that increased grid size carries increased risk [1]. The three U.S. grids provide an opportunity to test if reliability and efficiency are indeed a function of grid size. Theory aside, the matter of size enters into national energy pol- icy. Some have suggested that a major expansion (and upgrading) of the U.S. electrical system is needed, possibly integrating the regional grids into one national network. The prospect of replacing fossil fuel-generated electricity with generation from large-scale wind and solar installations may require new transmission lines to distant load centers. On the other side are proposals to divide the large grids into ten or twelve smaller areas, tied together with direct current connections, which would partially control cascading failures [2,3]. Wheeling is another factor that plays into the desire for an extensive versus modular grid system. For profit-making purposes, electricity traders want the ability to buy cheap electricity from one area and sell it at higher price in a distant area; this requires long-distance transmission lines. On the other hand, the farther electricity is sent, the more energy is wasted in line losses. Also, 0378-7796/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.epsr.2012.03.005