It was just an offhand number, there's already 17GW of storage in ERCOT's interconnection queue for the next few years, which is 40GWh - 70GWh. By 2035, the soonest we could expect to see a new nuclear reactor powering on, we will have many multiples of 70GWh. Not sure if TWh will every be needed for a grid that only peaks at 80GW. The cheapest solution will be a tradeoff between excess renewables capacity and storage, it will be interesting to see what the market picks for Texas.