I have family in TX as well, their power is on but their water is out. Main concern is keeping their horses watered, so they have been breaking the ice on a pond and hauling buckets.
What's interesting to me in all of this is how different things are here in Northeast PA, where we might have extreme cold, extreme heat, wind, floods, ice, snow and so on - so our "5 days of autonomous living" setup is just normal.
After chatting with my family, they said that after this is all over, they will definitely be working on a "5-day" setup covering the basics to keep their house alive. One problem they ran into is that some of their plumbing runs through their attic - an idea that blew my mind, but apparently happens there.