Here's What You Can and Can't Do With Walmart's Online Ordering Service

Walmart customers in 13 cities can now order their groceries online.

Walmart customers can order groceries online with free store pickup in 13 markets, the company announced today. The participating cities include Colorado Springs, Salt Lake City, Tucson, Atlanta, Nashville, Charlotte and Fayetteville, North Carolina, and Ogden, Utah. The company said it will expand the program to more cities in the coming weeks.

Walmart's online grocery orders don't require a subscription fee and same-day pickup is available for orders placed by 10 a.m. local time. Orders placed by 2 a.m. are ready for pickup at 8 a.m., and orders can be placed up to three weeks in advance. There is a $30 minimum per order.

The company first tested the service in San Jose, Calif., Denver, Phoenix and other markets.

Morningstar analyst Kenneth Perkins said Walmart's online ordering service was a smart move to boost sales.

"It's a cost-effective way to compete in the online channel and still leverage store real estate and drive traffic to stores," he told ABC News.

Other services like Peapod, founded in 1989, have long offered Internet grocery delivery services. Peapod, which works in partnership with Stop & Shop and Giant Food Stores, offers delivery services in 24 U.S. markets today. Fresh Direct, which serves the New York City and Philadelphia markets, charges at least $5.99 for delivery.