Ralphs Grocery Co. is joining a number of retail chains that have partnered with delivery service Instacart to bring groceries to customers’ doorsteps in the San Fernando and Conejo valleys.

“Offering home delivery powered by Instacart in Southern California is another way we are accelerating our digital and e-commerce efforts to create new and highly relevant customer experiences,” Kroger Chief Executive Rodney McMullen said in a statement. Ralphs is a subsidiary of Kroger.

The delivery initiative in Southern California was described as a pilot program that will be phased in through November.

Instacart, an Uber-like courier service for retailers, already offers same-day delivery to San Fernando and Conejo valley residents from such stores as Whole Foods, CVS, Gelson’s and Costco. Two-hour delivery fees start at $5.99 in most locations and increase with demand and shorter delivery windows. Instacart also offers an annual subscription for $149 a year, which offers customers free delivery on orders over $35.

Instacart makes money through delivery fees, revenue sharing with retailers and its subscriptions. The company raised $400 million in April through a Series D funding round and is valued at about $3.4 billion, according to business database Crunchbase.

Grocery chains are implementing on-demand home delivery in an effort to retain customers and keep up with Amazon Inc., which in many areas offers same-day delivery from Sprouts Farmers Market Inc., Gelson’s, and other grocers through Prime Now.

While some companies, like Kroger, have elected to sell their items through technology companies, others are staying in-house. Arcadia-based Vons Co. Inc., a subsidiary of Safeway Inc., has been offering delayed delivery for years, though it recently began allowing customers to book same-day service online.