The drill will not affect the general public unless a problem is encountered. If something needed repair or reinforcement, there would be a real-power shut down for however long it would take to correct the problem. During a power shutdown, we realize how much we depend on electricity to run our lives. Our food would perish without refrigeration, there would be no way to wash your clothes, no traffic signals and we would be living in complete darkness at night.
You can prepare for the drill simply just making sure that you have extra food on hand, batteries for flashlights, gas in your car, money, water and first aid supplies.
Check out a full article from the Houston Chronicle here: