Transferring energy between grids requires either converting it from AC to high-voltage DC and back using solid-state electronics, or converting it via mechanical energy using a variable-frequency transformer. With either approach, you need bulky and expensive equipment in proportion to how much power you want to handle. These connections are designed to smooth out (and profit from) short-term capacity fluctuations, not to power the entire state.

Currently, the Texas grid has two DC ties operating at full capacity and drawing about 800MW from the Southwest Power Pool. But that's a drop in the bucket compared to the ~45GW of current demand, or the estimated 70-80GW of demand that would be likely if it weren't for the outages.

http://www.ercot.com/content/cdr/html/real_time_system_condi...