August 2, 2019

Open Letter to Walmart CEO Doug McMillon about Skylights

Dear Walmart CEO, Doug McMillon: 

When government doesn’t step up, sometimes the makers of sustainable goods and services need a company as big as Walmart to create an economy of scale—essentially acting as an impact investor, albeit unintentionally. The commercial skylight market can thank your company for buttressing their industry for the past several decades. And all of us can thank Walmart for keeping tons (literally!) of extra CO2 in the ground—where it belongs—because of Walmart’s extensive use of skylights to illuminate your stores with sunlight.  

In the early nineties, Walmart recognized their need to reduce energy costs. Your company designed a new energy-efficient model store in Lawrence, Kansas. As a test, skylights were installed on half of the store’s rooftop; the other half had electric lighting. Surprisingly to your executive team (but not to lighting designers), the SKUs under the skylights sold much better than those under electric lights. To validate that merchandise lit by daylight sells better than under electric lighting, your Walmart store planners swapped the merchandise from one side of the store to the other—and discovered that the merchandise that didn’t sell as well under the electric lighting now sold better under the skylights.  

While the initial store test was implemented to reduce energy costs, the resulting increase in sales solidified your lighting decisions for years to come, inspiring your store planners to light stores with skylights going forward. 

How important was your company’s decision to favor skylights over electric lighting during daylight hours? Multiply one of your stores with hundreds of ceiling lights dimmed for 365 days of the year, times all of your stores, for a period of not years but decades. Now add in your enormous distribution centers. Walmart has a big footprint.

Because of Walmart’s role as a global leader, your company’s decision to use natural interior daylight over electric lighting has been mimicked by other major retailers. So, we also need to send some love to Home Depot, Kroger, and many others for their extensive and continued use of skylights.  

However, now that the cost of efficient LEDs has dropped significantly, will the sun set on your use of natural daylight? I hope not. Every ton of coal we burn for lighting—even LED lighting—expedites the day when extreme weather is no longer extreme. 

Major retailers are under tremendous pressure from online sellers. By acting responsibly, you invite us into your stores. And by installing skylights, you and other large retailers have a unique opportunity for a triple play: shrink energy costs, boost sales and tackle climate change—all at the same time. 

Sure, some retailers have harmed the environment, but I don’t expect capitalists to rein in unfettered capitalism on their own. Our job is to demand that corporations act responsibly with our dollars and to vote for elected leaders who understand that anthropogenic-caused climate change is the existential threat it truly is. We also need to recognize when you do the right thing, as with Walmart’s use of natural daylight to light your stores. 


Seth Warren Rose
Director, Eneref Institute

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