Back in 2011, environmental activist group Greenpeace had urged social network giant Facebook to stop using coal energy to power its servers – and as of late the global organization has been urging Apple Inc., amongst others, to also stay away from coal.

Greenpeace released a report called “How Clean is Your Cloud?” on Tuesday, which took a look at power consumption by various data center hubs. Though, the non-governmental organization apparently made some errors when accusing Apple’s Maiden, North Carolina facility of using up to 90% coal energy. Apple quickly contested this claim, citing that the fuel cell and solar power array it is building will become the largest in the country, and stated “We believe this industry-leading project will make Maiden the greenest data center ever built.” Apple hopes that 60% of the Maiden center power will eventually come from renewable energy sources. Greenpeace also overshot reality in its assumption concerning the amount of power consumption seen at the data facility – the organization claimed 100 megawatts, and Apple verified that it is 20.

Below are the general marks Green[eace handed out:

Of all the major data centers looked at, Google was given the highest renewable energy rating. While Facebook’s Swedish data center was praised for being powered by renewable energy sources altogether, the company received an overall mark of ‘C.’ Yahoo did alright, with a B average. Microsoft and Hewlett Packard received C’s, and Apple, Oracle< Twitter and IBM all got D's. At the bottom was Amazon, with an F. Amazon received bad marks all across the board, and it's likely a good thing that its cloud computing physical operation is only half the size of Google’s. Greenpeace has also in the past praised Google for conserving water while is cools its servers.