The leading corporate adopter of solar doesn't hail from California, as might be expected, but from Bentonville, Arkansas.

Wal-Mart had 142 megawatts of installed photovoltaic capacity as of 2015 and is chasing a 100 percent renewable power goal. Now the company is starting to lay out a strategy for energy storage.

The company has deployed 17 energy storage projects, all in the state of California, including six 200-kilowatt/400-kilowatt-hour solar-tied batteries. These systems currently serve the company with time-of-use shifting and peak demand shaving, said Mark Vanderhelm, Wal-Mart's vice president of energy, speaking to a crowd at the Energy Storage North America conference in San Diego last week.

There isn’t a specific timeline yet, but Vanderhelm said he is looking into future applications like frequency regulation, demand response, bidding into capacity markets, critical load backup power, and pairing with onsite generation for microgrid operation.

Vanderhelm envisions Wal-Mart stores becoming community hubs in the event of an emergency.

“We want to be a place to restart community after natural disaster,” he said. 

In an interview after the conference, Vanderhelm elaborated that “we don’t have a fixed commitment” in this regard, “but we’re thinking about it.”

The idea comes from previous events when Wal-Mart stores played a role in keeping community members safe in extreme weather events. 

Since Wal-Mart stores already have massive amounts of solar generation installed on their roofs and in their parking lots, and some stores even have functional microgrids in place, batteries would complete the circle of self-reliance. Diesel generators can provide a cheaper source of backup, but they often fail and can't work once the fuel runs out. Batteries could allow the solar system to disconnect from the grid and provide an additional source of clean backup power until the grid is restored.

It’s not clear what kind of monetary value the service would bring. But it would offer "another opportunity for us to take care of our customers" -- and, likely, to sell more stuff.

Combined with other grid service revenues, Wal-Mart's investment in storage could eventually be a real money-maker. 

“It comes down to the right combination of partners and value propositions,” Vanderhelm said. “We’ve done this in LEDs, we did it in solar and we’d really like to do it with storage.”

If that happens, Wal-Mart could single-handedly break open the U.S. commercial and industrial storage sector, which has deployed 50.7 megawatts since 2013, according to GTM Research.

Wal-Mart has more than 5,000 stores in the U.S. If only 250 of them deployed the 200-kilowatt batteries that some locations have already installed, that would equal today's cumulative total C&I storage deployments.