Being environmentally friendly has become big business. It is, of course, the right thing to do - but beyond that, it has become an institutionalised concept. And for the green movement, that's not a bad position. Most new buildings are designed from the ground up with environmental concerns at the forefront. A company that is able to advertise itself as "green" gets public relations points, politicians get extra votes for promoting the green agenda, and individuals talking up the green position are no longer limited to a small group of long-haired folk singers. Being green has, in short, become part of the mainstream.
Or is it? Skepticism abounds, and green claims are largely anecdotal and based on a set of claims that are difficult to measure on a macro level.
Grail Research’s 
report, “Cloud computing: Fact versus fog” attempts to take an unbiased look at the cloud. Here are the facts. Green claims come from two different areas. First, many large data centres support their claims to being energy-neutral not by drawing against alternative energy sources, but rather, by purchasing carbon credits. It would in fact, be highly unlikely that a data centre would be able to deliver service whilst drawing power against nothing but windmills and solar panels - the high levels of reliability demanded by customers virtually require connection to the power grid. In fact, a cloud data centre does consume an enormous amount of energy, and the green claim may be little more than an accounting trick that purchases somebody else’s efficiencies.
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The windmills and green colour schemes featured on cloud centres’ websites may be all hype, but beyond the outward image and the cabon credits, there may well be something to the green claim. Some skeptics claim that the cloud doesn’t actually save power, but merely centralises it, allowing several companies to use less energy while the cloud provider actually uses more. In the end, they say, it comes out in the wash.
That said though, arguments in favour of the green cloud deliver the indisputable fact that cloud computing companies are typically based on a virtualised data centre, which enjoys a higher utilisation rate than a standard data centre. There can be little doubt that virtualisation saves energy, since it avoids the occurrence of over-provisioning, thereby achieving a net gain in power efficiency. In addition, the scalability afforded by the virtual hardware environment allows the end users to scale up and down on demand, reducing their own usage and carbon footprint.
The actual energy balance sheet has yet to be reported, but we can draw some conclusions from observation. Cloud data centres are very likely to consume increasingly large amounts of energy, which displaces energy used by end users. On balance though, an efficiently run cloud centre serving a large number of clients with scalable, on demand resources would appear to enjoy a net gain in energy efficiency when compared with an alternative of multiple, over-provisioned on premise centres.