Icing on power lines was only one of the issues during that time. Among the problems, the cold actually shut down power plants themselves. And a huge increase in residential natural gas use caused the utilities to shut down many natural gas fired power plants to divert natural gas to their residential customers. (I get the impression that the hassle and danger of turning on millions of pilot lights for residential natural gas customers was a bigger concern than letting the gas fired power plants shut down.) This article describes that episode and how the blackouts happened. It says that 50 Texas power plants dropped off the grid. The wholesale price of electricity spiked from $70 MW/hr to over $3,000.

The article also mentions the deregulated Texas power market. The energy companies aren't required to build enough power plants, or even any power plants, if they can get their power from someone else. That's why the shutdown of gas-fired plants in the next few years will happen in Texas, as I mentioned in my previous post.

As long as there is just enough power to meet demand, then prices will remain too low for these Texas energy companies to have a financial incentive to make those expensive upgrades to those gas fired plants. Therefore, any sudden loss of capacity, like that winter episode, or a sudden spike in demand will lead to blackouts.