Utilities retain "reserve margins" of extra generating power for summer peaks and for unanticipated incidents when power plants are forced to shut down. A reserve margin provides protection against brownouts and blackouts. Regional grids like to maintain reserve margins of at least 15 percent, meaning they have 15 percent extra capacity at any time in case of a shutdown.

Most regions of the country now have excess reserves, according to figures released this week by the Energy Information Administration. The map shows the country's 14 regional grids. The figure on the right is the targeted reserve margin and the figure to the left is the actual reserve available as we enter the summer of 2012, always the period of peak use. Most of the regional grids in the eastern portion of the country are highly interconnected and can send power back and forth in case of shortages.  All now have spare capacity and many have almost twice the targeted reserve.

Texas is the one region that may experience power shortages this summer. Texas' ERCOT grid is isolated because Texas traditionally worried that other parts of the country would requisition its electrical production at below-market rates as the country had done for many decades with natural gas.  Now with the economy thriving, coal plants closing and nuclear development on hold, Texas is running short of electricity. Demand almost exceeded supply last year on several 100-degree days and very little new capacity has been added since then.

California is in similar straits because of the shutdown of the San Onofre reactors, which provided 5 percent of the state's electricity. The reactors will probably not be back up this summer.

Finally, New York has only a slim margin because it has resisted all kinds of new construction. But New York is well plugged into the New England grid and is not likely to run short - unless Vermont decides to close down the Vermont Yankee reactor in the near future. Both New York and New England are talking about building transmission lines north across the border to tap into James Bay hydroelectricity. The New York line would run straight down the Hudson River into New York City.

The current excess in reserves is due almost entirely to the lagging economy and the slowdown in industrial and commercial activity.  Yet as the Energy Information Administration warns, "building new generating capacity can take years" and is best done long before shortfalls begin to appear.  If economy activity were to pick up again, all this excess reserve could quickly disappear.