The report – The Cloud Begins With Coal: Big Data, Big Networks, Big Infrastructure and Big Power – is written by Mark Mills, CEO of Digital Power Group, a tech-industry advisement firm. It was sponsored by the National Mining Association and the American Coalition for Clean Coal Energy.

The study claims that for the world to continue to use digital devices, such as smartphones and tablets, at the same rate, an enormous amount of energy will be required – and can only be adequately and reliably provided by an equally large amount of coal mining.

Mills claims global IT infrastructure – from smartphones to laptops and digital TVs – uses 1500 terawatt-hours of power per year, "equal to all the electric generation of Japan and Germany combined", and about the same amount of electricity used to light the entire planet back in 1985.

Mills also claims his research shows that watching an hour of video per week on a smartphone or tablet "consumes annually more electricity in the remote networks than two new refrigerators use in a year."

Mills reports that a medium-size refrigerator will use about 322kW/h a year and the average iPhone, according to Mills’ calculations, uses about 361kW/h a year once the wireless connections, data usage and battery charging are added. This will only increase as more people move towards the technology.

And in order to meet future electricity demands, more coal mining is needed.

“In every credible forecast – including from the EIA, IEA, BP, Exxon – coal continues to be the largest single source of electricity in the world,” the report states.

“Coal’s dominance arises from the importance of keeping costs down while providing ever greater quantities of electricity to the growing economies, and as the IEA recently noted, the absence of cost-effective alternatives at the scale the world needs.”

While the idea that electricity use will rise and coal is an available and reliable source to meet this demand is accurate and has not been disputed, a number of researchers have identified problems in Mills’ report, claiming that he has used outdated information and overstated figures sourced from other research.

For example, Mills use a graph that Greenpeace produced in 2012 that shows a high dependence on coal for cloud data center companies, such as Apple and Facebook.

However, many of these companies have transitioned towards renewable energy – with Apple's data centers, for example, now 100%-powered by renewable energy from a solar farm in North Carolina, according to the company’s most recent environmental report.

Jonathan Koomey, a research fellow at the Steyer-Taylor Center for Energy Policy and Finance at Stanford University, has been analyzing Mills’ reports since the mid-1990s.

Following the release of The Cloud Begins With Coal, Koomey posted a statement on his blog warning the industry and media of Mills’ research.

“Mark P Mills has reappeared, and remarkably is repeating some of the same wild claims that we debunked last time (circa 1999-2003),” Koomey wrote Monday.

“Mills has made so many incorrect claims that he simply shouldn’t be treated as a serious participant in discussions about electricity used by information technology equipment.

“He cherry picks numbers to suit his narrative, and creates the appearance of doing real research by including many footnotes, but almost invariably he overestimates the amount of electricity used by IT equipment. Last time many important people were misled by his antics–I hope they are smarter this time.”

A study published by Koomey in 2004, states that Mills’ claim that “the “behind-the-wall” networking, server, and switching equipment needed to support a wireless personal digital assistant used as much electricity as a residential refrigerator” was incorrect and “too high by a factor of two thousand”

“We investigated these claims and in virtually every case they represented overestimates of electricity used by office equipment,” Koomey wrote in the epilogue to his 2008 book, Turning Numbers into Knowledge.

“One would expect to find small differences between any such estimates, but when errors are all large and in the same direction it is likely that there is a bias in the analysis.”

In a statement emailed to MSN News, Mills has defended his research saying that "at least a dozen" scholarly articles give similar estimates for power usage.

“None of the data in my report are new or original — this was a technical literature search study,” Mills said.

“And finally, the point of the title (and sponsors) we pedantically noted ... there are NO recommendations on how to make electricity; it is simply a fact that coal is the largest global source.”