Across the sprawling parking lots and expansive rooftops of America’s retail corridors lies a massive, untapped opportunity to accelerate the nation’s transition to clean energy. Experts suggest that if the U.S. Leveraged the rooftop solar potential of big-box stores, it could slash planet-warming emissions and save companies millions of dollars in operational costs.
The scale of this potential is immense. According to a report from the nonprofit Environment America and research firm Frontier Group, big-box stores and shopping centers possess enough roof space to generate half of their annual electricity needs through solar power. Fully utilizing this space would produce enough electricity to power nearly 8 million average homes and would have an environmental impact equivalent to removing 11.3 million gas-powered cars from the road.
Despite these figures, only a fraction of these retail giants have fully committed to on-site solar. While some have made strides, the gap between theoretical capacity and actual installation remains wide, driven by a complex mix of structural hurdles, disjointed federal policy, and a corporate hesitation to deviate from traditional business models.
The financial incentive is already proven in specific cases. At an IKEA location in Baltimore, the installation of solar panels on the roof and across the parking lot reduced the store’s purchased energy by 84% and cut costs by 57% between September and December of 2020, the company reported. By February 2021, IKEA had installed 54 solar arrays, covering 90% of its U.S. Locations.
The Scale of Untapped Energy
The sheer physical footprint of the American superstore makes it a prime candidate for energy generation. A typical Walmart store, for instance, features roughly 180,000 square feet of rooftop—an area comparable to three football fields. According to the Environment America report, a single such roof can support enough solar energy to power approximately 200 homes.
When scaled across the entire retail landscape, the numbers become staggering. Walmart alone, with around 5,000 U.S. Stores, possesses more than 783 million square feet of rooftop space—an area larger than Manhattan. This represents an annual rooftop solar potential of more than 8,974 gigawatt hours, enough to power over 842,000 homes.
| Retailer | Estimated Households Powered |
|---|---|
| Walmart | 842,700 |
| Target | 259,900 |
| Home Depot | 256,600 |
| Kroger | 192,500 |
| Costco | 87,500 |
Johanna Neumann, senior director for Environment America’s campaign for 100% Renewable, argues that the failure to utilize these spaces is a systemic waste. “Every rooftop in America that isn’t producing solar energy is a rooftop wasted as we work to break our dependence on fossil fuels and the geopolitical conflicts that arrive with them,” Neumann said.
Structural and Policy Roadblocks
If the benefits are so clear, why is adoption so slow? For many retailers, the answer lies in the physical state of their infrastructure. Craig D’Arcy, director of energy management at Home Depot, noted that aging rooftops are a “huge impediment.” If a roof requires replacement within the next 15 to 20 years, the company finds it does not make financial sense to install solar systems immediately. Home Depot currently has 75 completed rooftop solar projects across its approximately 2,300 stores, with 12 more under construction.
Similar constraints exist for other giants. Kroger, which operates about 2,800 stores, has solar installations at 15 properties, including distribution centers and manufacturing plants. A company spokesperson cited the structural ability of roofs to support such installations as one of several factors affecting viability.
Beyond the physical roofs, critics point to a “disjointed” regulatory environment. Rep. Sean Casten of Illinois, who co-chairs the House power sector task force, argues that federal policy has historically subsidized fossil fuel extraction while penalizing clean energy production. Casten noted that for a long time, local utilities often acted as a barrier to rooftop solar because they did not want to lose the “load” or the revenue from the customer.
Edwin Cowen, a professor of civil and environmental engineering at Cornell University, suggests that the complexity of hiring local firms that understand specific municipal policies adds another layer of friction. “It’s just another layer of complexity that I think is beginning to make sense because the costs have come down enough, but it needs kind of reopening that door of getting into an existing building,” Cowen said.
The Social Equity Dimension
The transition to retail solar is not just about corporate balance sheets; it is also a matter of social and economic equity. Advocates argue that a “solar revolution” in the retail sector could provide a windfall for marginalized communities, who often suffer disproportionately from the effects of the climate crisis and extreme heat.
Charles Callaway, director of organizing at WE ACT for Environmental Justice, suggests that the impact would be magnified if companies prioritized local labor for installations. Callaway has led worker training programs in New York City, training over 100 community members—primarily people of color—to become solar installers. He also formed a solar workers cooperative to ensure these trainees find stable employment.
Jasmine Graham, energy justice policy manager at WE ACT, emphasizes that the potential is only truly encouraging if projects pay prevailing wages and utilize “community solar” models. Such models would allow residents in the same utility zone to receive discounts on their electricity bills, effectively sharing the benefits of the big-box store’s roof with the surrounding neighborhood.
Current Corporate Progress
While the gap remains large, some retailers are moving toward renewable targets. Target ranked first for on-site solar capacity in 2019, according to the Solar Energy Industries Association. A company spokesperson stated that Target now has 542 locations with rooftop solar—roughly a quarter of its stores—which meet between 15% and 40% of those properties’ energy needs.
Walmart has reported completing on- and off-site wind and solar projects with a capacity to produce more than 2.3 gigawatts of renewable energy. As of the end of the 2021 fiscal year, the company had installed nearly 194 megawatts of solar capacity on its U.S. Facilities. The company has stated its aim is to source 100% of its energy through renewable projects by 2035.
Costco CFO Richard Galanti reported that the company has 121 stores with rooftop solar globally, with 95 of those located in the United States.
As the window for climate action narrows, the pressure on these retail giants to convert their “wasted” rooftops into energy generators continues to mount. The next major milestone for these companies will be the progress reports toward their 2030 and 2035 renewable energy targets, as well as potential shifts in federal incentives for commercial solar adoption.
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