Amazon Web Services has been under fire in recent weeks from a group of activist customers who are calling for the company to be more transparent in its usage of renewable energy.
In response, rather than divulge additional details about the source of power for its massive cloud infrastructure, the company has argued that using the cloud is much more energy efficient than customers powering their own data center operations.
But the whole discussion has raised the question: How green is the cloud?
In early June a pact of 19 AWS customers including Hootsuite, Change.org and Tumblr - wrote Amazon Senior Vice President Andy Jassy requesting increased transparency in the company's efforts to use clean energy.
The letter was in response to a report from environmental activist group Greenpeace, which singled out Amazon Web Services, saying "no company could do more" to help tech companies be more energy friendly than AWS. The company's cloud platform hosts so many popular websites that any steps it takes to increase efficiency would benefit many other companies.
"Amazon Web Services is holding many of our favorite sites hostage to dirty energy," the report notes. Specifically, it says AWS's US East region, located in Virginia, houses 60% of the company's servers and uses a mix of about one-third coal, one-third nuclear, one-fifth gas and only 2% renewable energy.
In response, the next week AWS announced plans to build an 80 megawatt solar farm in Virginia. Company officials are on the defensive again this week, releasing figures saying that overall, its cloud platform runs on 25% renewable energy, with a goal of using 40% renewable energy by 2016, and eventually 100% green power.
Greenpeace says that's not enough. "It remains impossible for its customers or the public to benchmark any progress toward that goal, since the company refuses to disclose any of its energy data," the report states.
AWS officials argue that the simple fact that so many customers use the company's cloud is saving energy. AWS is more efficient at running data centers compared to its customers, even if it uses fossil fuels to power those data centers, AWS Distinguished Engineer James Hamilton contends in a blog post.
AWS says customers use 77% fewer servers and 84% less power by running their workloads in its cloud compared to their own data centers. That creates an 88% reduction in carbon emissions for customers who use Amazon's cloud, AWS Evangelist Jeff Barr's blog post says.
Furthermore, the company's US-West location in Oregon, its EU region in Frankfurt and its GovCloud region in the U.S. are what the company calls "carbon-neutral" which refers to the practice of offsetting the amount of carbon the site is responsible for with the purchase of a corresponding number of carbon credits that fund green projects. And AWS is building a 150 megawatt wind farm in Indiana.
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