The Houston Chronicle published an article on the cost of building additional transmission capacity to connect wind power in West Texas with the major cities in the state, see link below.
The transmission study prepared by ERCOT proposed five options, according to the article
"The least expensive option would cost $2.95 billion and calls for 5,150 megawatts of new wind power that would require about 1,600 miles of new power lines. The most expensive would cost $6.38 billion, could handle 17,956 megawatts of new wind power and calls for 3,000 miles of new lines."
Just to give you an idea of scale of additional capacity ERCOT plans to add, the system currently has a west to east transfer capacity of only 3,200 megawatts (according to the Nuts and Bolts of Wind Integration report on the ERCOT website, see link below).