Amazon, Apple and Twitter were graded poorly Tuesday in a Greenpeace study of technology titans' use of clean energy to power the mushrooming Internet cloud, but Facebook, Google and Yahoo! won praise.

The environmental charity's "How Clean is your Cloud?" report, billed as a rallying cry instead of a critique, related to the companies' use of data centers and other energy issues.

"We are not trying to give them a hard time, we are trying to build them up to do the right thing,"Greenpeace senior campaign specialist Casey Harrell told AFP.

"We love our iPhones, they make our lives better; but they shouldn't make the planet worse."

Cupertino, California-based Apple got "D" grades for efficiency of datacenters, sharing information about power use, and lobbying utilities to provide clean energy.

Apple was given a flunking "F" when it came to locating datacenters in places where electricity comes from clean sources instead of climate-ruining coal.

Apple, however, rejected the Greenpeace findings as outdated or flat-out wrong, and said it was leading the pack when it comes to shifting datacenters to clean energy.

The company's new North Carolina datacenter aims to get more than 60 percent of its power from renewable sources including an on-site solar farm and a fuel cell installation touted as the largest of their kind in the United States.

The facility will be "the greenest datacenter ever built" and will be joined next year by one in Oregon powered completely by renewable energy, according to Apple spokeswoman Kristin Huguet.

Amazon.com and its cloud-based Amazon Web Services got failing grades in all but datacenter energy efficiency, where it got a "D."

Technology firms tend to be tight-lipped about datacenter power use for competitive reasons, and Amazon.com said the information about it deduced by Greenpeace was "inaccurate."

"Amazon Web Services believes that cloud computing is inherently more environmentally friendly than traditional computing," the company said in response to an AFP inquiry.

"Instead of each company having their own datacenter that serves just them, AWS makes it possible for hundreds of thousands of companies to consolidate their datacenter use into a handful of datacenters in the AWS Cloud."

While datacenter efficiency is a worthwhile goal, switching to clean energy is needed to safeguard the health of the planet, according to Greenpeace.

The trend of software hosted in the Internet "cloud" to provide services such as Web-based email, video viewing, picture sharing, social networking and "tweeting" is driving demand for datacenters.

If the world's datacenters were considered a country, it would rank fifth when it came to electricity consumption in a global ranking of nations, according to Greenpeace.

A major factor in locating datacenters has been cheap electricity, resulting in them being built in places where utilities generate power by burning coal, a prime source of climate changing carbon gas emissions.

Datacenters are so coveted as customers by power companies that technology companies have clout to press for a switch to clean energy sources, according to Greenpeace.

"The explosive growth of datacenters is a big problem if it continues to be linked to coal, or a big opportunity," said Greenpeace media officer David Pomerantz.

"If the IT sector pushes to bring solar, wind and other renewables online it could be a huge game changer."

Google has been investing aggressively in renewable energy. Facebook in December implemented a policy making the availability of clean power a criterion for where it builds datacenters.

"We've put a significant time and resources into making Google as energy efficient as possible, using renewable energy, and investing in the sector," said Google senior vice president for technical infrastructure Urs Hoelzle.

"We welcome reports like this, as they bring additional attention to these important issues for the industry."

Internet pioneer Yahoo! was an early adopter of putting datacenters in places with renewable energy sources.

The list of companies graded included IBM, Microsoft, Hewlett-Packard, Oracle, and Salesforce.com.

"These guys aren't the enemies," Pomerantz said of the 14 technology firms graded.

"The enemies are the Duke Energy(s) of the world blowing up mountains to provide power," he added.