To the standard reasons to move to the cloud—greater scalability, reduced administrative costs, improved availability—Microsoft is hoping to add another reason: a lower carbon footprint. A new, Microsoft-sponsored study suggests that small businesses can reduce their carbon footprint by up to 90 percent by switching from on-premises Exchange, Sharepoint, and Dynamics CRM to cloud-hosted alternatives.

The argument makes sense; small businesses tend to have servers with capacities greatly in excess of their needs, leading to a lot of waste—an idle server may use 50-60 percent of the power of a fully-laden one. Cloud service providers use multi-tenancy to ensure that their servers run with little spare capacity, getting far more useful work out of each ton of carbon dioxide. Their specialization also allows them to build data centers with higher efficiency than conventional standalone servers.

The gains for larger organizations with 10,000 or more users were accordingly far smaller: larger organizations tend to push their servers harder, making them more efficient. But even for these, reductions in the range of 20-80 percent are claimed, depending on workload. The study suggests that if every US company with between 100 and 10,000 employees were to switch its e-mail service to a cloud-hosted alternative, the total carbon emission saving would be equivalent to taking 100,000 passenger cars off the road.

Data centers are already a significant user of electricity, and a greater switch to cloud computing will make them even more power-hungry. Their greater efficiency, however, means that the use of cloud services could still be a net win. While carbon savings are unlikely to be a significant factor in the thinking of all but the most environmentally conscientious of corporations, the greenwashing potential of the study's findings could yet stimulate greater cloud adoption.