A Microsoft/Accenture/WSP report compared three applications used in-cloud and on-premises. A Google report takes a similar look at Google Apps. Both claim CO2e reductions ranging above 80%. Pike Research says the move to cloud computing will decrease overall data center GHG emissions by 28%. The most recent report, a WSP/NRDC study, reinforces these themes but offers balancing perspectives.

Microsoft

Said Microsoft in 2010,"Though large organizations can lower energy use and emissions by addressing some of these factors in their own data centers, providers of public cloud infrastructure are best positioned to reduce the environmental impact of IT because of their scale." The 2011 report compared application use in three different sizes of enterprises, with smaller ones showing the greatest relative benefits:

The analysis suggests that, on average across the different applications, typical carbon emission reductions by deployment size are:
• More than 90 percent for small deployments of about 100 users
• 60 to 90 percent for medium-sized deployments of about 1,000 users
• 30 to 60 percent for large deployments of about 10,000 users

Enabling Technology, a European initiative supported by Microsoft, calculates, "If 80% of all organizations within European Union (EU 27) that currently use on-premise servers to deliver email, customer relationship management and groupware to their employees adopted cloud computing instead, the estimated savings would be…5,054,385 tonnes of carbon dioxide emissions saved every year…$2,819,327,072 in reduced energy expenses every year."

Google

Google also reported dramatic cloud advantages in 2011: "…the annual carbon footprint of a Gmail user is about 1/80th that of a small business with locally hosted email servers…For a small office of 50 people, choosing Gmail over a locally hosted server can mean an annual per-user power savings of up to 170 kWh and a carbon footprint reduction of up to 100 kg of CO2. Larger organizations show smaller, though still impressive efficiency gains."

Google provided more data in June 2012. "Last year, we crunched the numbers and found that Gmail is up to 80 times more energy-efficient than running traditional in-house email. We’ve sharpened our pencils again to see how Google Apps as a whole—documents, spreadsheets, email and other applications—stacks up against the standard model of locally hosted services. Our results show that a typical organization can achieve energy savings of about 65-85% by migrating to Google Apps." (The company claims Google Apps at US GSA reduce energy 90%, CO2e 85%.)

Pike

Pike Research reinforces these assessments from a macro perspective:

Growth in cloud computing has some important consequences for both greenhouse gas (GHG) emissions and sustainability. Thanks to massive investments in new data center technologies, computing clouds in general and public clouds in particular are able to achieve industry-leading rates of efficiency. Simply put, clouds are better utilized and less expensive to operate than traditional data centers…only the very largest of organizations – both commercial and governmental – will have the capital and expertise to achieve a similar level of efficiency at a comparable cost. As a result…much of the work done today in internal data centers will be outsourced to the cloud by 2020, resulting in significant reductions in energy consumption, associated energy expenses, and GHG emissions from data center operations versus a business as usual (BAU) scenario.

Specifically, Pike calculates

…data centers will consume 139.8 terawatt hours (TWh) of electricity in 2020, a reduction of 31% from 201.8 TWh in 2010. This also represents a significant decrease from the 226.4 TWh that would be consumed by data centers in the firm’s BAU scenario. The reduction will drive total data center energy expenditures down from $23.3 billion in 2010 to $16.0 billion in 2020, as well as causing a 28% reduction in GHG emissions from 2010 levels.

Pike anticipates worldwide cloud computing revenue increasing from $46.0 billion in 2009 to $210.3 billion by 2015, a CAGR of 28.8%.

WSP/NRDC

An October 2012 WSP/NRDC report found, "…half of the servers in the United States still reside in smaller server rooms and closets which are typically managed less efficiently than large data centers. Furthermore, the scale of large cloud computing service providers already gives them a strong incentive to optimize energy management as energy represents a significant component of their operating expense – this is not necessarily the case with smaller cloud providers or a SMO’s [small or medium organization's] on-premise solution." The report does caution that "…this is not always the case and exceptions exist. Many factors contribute to the energy- and carbon-efficiency of both on-premise server rooms and cloud services. The most efficient server rooms can have significantly lower environmental impacts than the least efficient cloud services." The report's aim to to provide SMO IT managers with information leading to more sustainable operations.