Amazon Web Services, the largest public cloud around, has started a pilot of the new stackable battery units Tesla unveiled today, under the new Tesla Energy brand.

“We’re excited to roll out a 4.8 megawatt hour pilot of Tesla’s energy storage batteries in our US West (Northern California) Region,” James Hamilton, distinguished engineer at AWS, said in a statement in press materials for today’s product launch. “This complements our strategy to use renewable energy to power our global infrastructure.”

In November, AWS committed to running exclusively on renewable energy. The division of Amazon.com announced in January that it’s supporting the development of a wind farm in Indiana.

In today’s statement, Hamilton explains that batteries can “help bridge the gap between intermittent production, from sources like wind, and the data center’s constant power demands.”

Tesla says its new batteries can provide several benefits to businesses, including buying power at the lowest possible rates and providing backup. Data centers typically operate with backup generators on hand and ready to go; this provides some of Amazon’s data centers with another option.

The Tesla batteries could provide Amazon with a new competitive advantage as it challenges other cloud providers, like Google and Microsoft, in a market where the slightest cost savings can make a difference.