COVID-19 convinced a lot of consumers to try online grocery shopping for the first time, and many plan to keep buying food that way long after the viral threat has receded and they’ve put their face masks and hand sanitizer away.

Already more consumers say they are shopping online because it is easy and convenient (76%) than because they want to avoid potential COVID risks (59%), according to a recent survey by ACI Worldwide and PYMNTS.

“While the pandemic drove an undeniable shift to digital shopping, it’s clear that consumers are more likely to continue to use these methods due to their ease and convenience than for the safety reasons that initially led them there,” ACI Worldwide executive vice president Debbie Guerra said. “These consumers have discovered the benefits of digital shopping and like what they’ve found.”

Most people continue to buy their groceries the old fashioned way, by going into the store and picking items from the shelves. Ninety-four percent of consumers report that they shop in-store at least some of the time, according to the survey of 2,342 adult U.S. consumers. But 34% of consumers shop for at least some of their groceries online, and that share jumps to 57% among Millennial shoppers.

The survey found that 23% of shoppers use home delivery, and 8% say it is their preferred channel. Curbside pickup is used by 20% of shoppers, with 7% calling it their favorite option.

Other research, meanwhile, suggests that retailers should consider exactly what convenience means to their customers.

For many consumers, speed is less important than being able to select a specific delivery day and time. According to a new analysis, a typical grocery customer would happily wait more than 10 hours more for a delivery if the delivery window was one hour shorter, and would wait an extra 7.5 hours longer if they could receive the delivery on a preferred day of the week.

Moreover, customers’ delivery preferences can vary depending on such factors as basket size and how loyal the shopper is to a particular retailer. Repeat customers are willing to pay more for the same delivery attributes than other shoppers, for example. And customers with very large baskets are willing to pay double the delivery fee to improve delivery-window precision by one hour.

“Analytically minded retailers can craft delivery time slots that are unique to each customer based on revealed preferences,” says Nicole DeHoratius, adjunct professor of operations management at the University of Chicago Booth School of Business. “I strongly encourage retailers to rethink their operations to optimize not only on speed but also the most appropriate combination of speed, precision and ­flexibility.”