ERCOT numbers show about 75,000 MW of generation availiable.
http://www.ercot.com/content/news/presentations/2010/ERCOT-2010-Capacity-Demand-and-Reserves-Report-Winter-Update.pdf
See post 80.
Showing the ERCOT boundaries [in blue] where the rolling blackouts occurred except for El Paso Electic which isn't a part of ERCOT.
ERCOT in relation to the rest of the US as far as electric grids are concerned. Texas chose to remain instate with their grid with no major ties to the other US grids to keep the FERC out of control.