Tim and Debbie Hennessy told ABC News they were two among hundreds of shoppers at an H-E-B store in Leander when the power went out.
A clerk told the couple to take their items to check out, but after about 15 minutes of waiting in line, the people ahead of them started to move quickly, Tim Hennessy wrote in a Facebook post.
He said the woman at checkout first asked if they had any alcohol.
"I said, 'No, but if you are giving out drinks, I could use one about now.' She then said, 'Please go ahead, but we can't bag anything up for you.' At first, Deb and I were a bit confused and I asked, 'How or who do we pay for our groceries?' We probably had a couple of hundred dollars worth of groceries. She said, 'Just go ahead and be safe driving home," Tim Hennessy wrote.
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He said the store's generosity made him and his wife tear up.
"This is the America that I know. Despite all the negative we hear/see being reported daily in the news. America and most Americans are still kind, thoughtful, generous, and caring," he wrote.
Power outages spiraled throughout Texas amid last week's winter storms, forcing hundreds of grocery stores to shut down. At locations that remained open, customers complained of long lines outside and then empty shelves once brimming with water, bread and milk when they got inside.