• Target has turned a California location into its most sustainable store.
• Solar panels on the roof and carports will power the entire store, from its refrigeration to its heating and air conditioning.
• It could become a new model for the national retailer, as it sets goals to reduce carbon emissions and works to signal to customers and investors that it's serious about sustainability.

Target has rolled out one of the most visible displays of its efforts to become a greener company: Massive carports topped with solar panels that will power a big-box store in California.

The panels, high above the parking lot, will produce enough renewable energy to power the entire store, from its refrigeration to its heating and air conditioning, the retail chain says. And the towering structures outside offer a striking visual clue into the environmentally conscious efforts going on inside the store.

In aisles with items like milk, ice cream and frozen pizza, refrigerators and freezers will use a natural refrigerant to cut back on emissions. All sales floor lighting has been replaced with LED, and back outside, customers who arrive in electric cars can charge them in the parking lot.

The Target location in Vista, Calif., about 40 miles north of San Diego, has become the company's most sustainable store — and could become a national model for the retailer. Target previously installed solar panels on the location's rooftop, which power a portion of the store.

John Conlin, senior vice president of Target properties, said the retrofit makes the location the company's first net-zero energy store. The chain expects the solar panels to produce 10% more energy than the store needs, which it will return to the local power grid.

"This is a big step for us in terms of how we're testing and learning from innovations around sustainability," Conlin said.

Conlin, who oversees store remodelings and build-outs of new facilities, said the features could eventually be added to other locations in the chain. The company currently maintains solar panels on roughly 25% of its approximately 1,900 stores.

Target has said it wants to source 100% of its energy from renewable options by 2030 and plans to reach net-zero carbon emissions by 2040.

Last week, it debuted a new Target Zero icon that it will use to highlight products in stores and online that are designed to be refillable, reusable or compostable.

At the Vista store, Conlin said, customers will see explanations about behind-the-scenes green features that will inform them about the company's switch to the natural refrigerant.

A Target spokesman said the company will receive a one-time federal tax credit as part of the project.

For employees and customers, the carports will serve an additional purpose: coverage on sweltering or foul weather days for its Drive Up curbside pickup service, one of the company's top growth drivers for its e-commerce business over the past two years.

Environmental advocacy organizations have urged big-box and grocery stores to add more solar panels to their locations, saying the companies could dramatically expand the country's supply of renewable energy because of their massive square footage.

A report in January by two nonprofits, the Environment America Research and Policy Center and the Frontier Group, estimated that with rooftop solar panels, retailers could generate enough clean electricity to power more than 7.9 million U.S. homes. That would be roughly equivalent to taking more than 11.3 million cars off the road, the advocacy groups said.

Johanna Neumann, a senior director at Environment America Research and Policy Center, said too many retailers are pledging to purchase more renewable energy without taking the step to become clean energy producers with rooftop solar panels. She called the disconnect "a huge missed opportunity."

"It's such a no-brainer," she said. "Some retailers understand that value and are leading the way, but we're just scratching the surface."

The nonprofit has lobbied for more tax breaks that encourage installation, but Neumann said she would like to see retailers step up — even in states where the solar panels require a bigger investment.

Home Depot has solar panels on more than 70 of its stores. Lowe's maintains rooftop panels at four locations. Both home improvement retailers told CNBC they plan to install more panels in the near future.

Walmart says it has implemented more than 550 renewable energy projects, but didn't specify how many involve rooftop solar. In a statement, the company said it aims to be powered by 100% renewable energy by 2035 — and estimates it's at 36% today.

Some restaurants, too, are pushing solar panels to help reach their sustainability goals. Salad spot Sweetgreen and Restaurant Brands International's Burger King are among the chains that have unveiled new restaurant designs that include solar panels. And McDonald's opened a location in Walt Disney World Resort that is entirely run on solar energy from roof and glass panels.

—CNBC's Amelia Lucas contributed to this story.