Now, before you start thinking the higher-ups at Walmart have suddenly seen the green light, it's a little more complicated. Basically, the suits were able to flex their muscles to get a really good deal from the solar company -- they put up shiny shingles all over middle America's favorite store, and in return, Walmart got access to the generated power at a discount. The solar company got a lot of sun and a permanent long-term customer, and Walmart was able to drastically reduce energy consumption in their stores. The fact that all this is good for the environment seems to be a coincidental side effect. I'm pretty sure Walmart would use door greeters as batteries like in The Matrix if it were actually energy efficient.
"We don't know who struck first, us or them, but we know that it was us that scorched the sky."
However, though it's probably just a numbers game, there's no denying that it's a net gain for the planet -- even if some of their energy comes from solar, that's no chopped liver for a company whose electric bill is a goddamn billion dollars a year. Plus, the whole point is that other huge companies would see their example and want to do this, even if it's just for financial reasons. Which is why, since that chart was published a couple years ago, Target has caught up, installing 70 MW of power in 2016 alone. The fact that this makes Mother Nature happy is just a bonus in the grand scheme to sell as many pairs of Avengers pajamas as possible.