Walmart Inc. WMT, -0.47% said Tuesday that it will offer online grocery delivery to more than 40% of U.S. homes through a partnership with Postmates, the on-demand delivery service that launched in 2011. The expansion will start in Charlotte, N.C. and spread in the coming months. Walmart personal shoppers will pick the groceries customers select online or on the Walmart app and select a delivery window for Postmates to bring the items to the shopper's home. Groceries can be delivered same-day, there's a $30 minimum order, and a $9.95 fee for the delivery services. The first order will be free with a $50 minimum and a special code. Currently, Walmart orders a free service at 1,200 stores that allows customers to order online and pick up their groceries curbside. That program will add another 1,000 stores this year. Walmart shares are up 1% in premarket trading, and up more than 18% for the past year. The Dow Jones Industrial Average DJIA, +0.19% is up 16.1% for the last 12 months.