Vodafone were among the companies receiving the most favourable ratings in the latest Greenpeace 'Cool IT' index of the technology sector's energy practices.

The latest edition of the Greenpeace ratings showed tech companies are not just making their products less carbon-intensive; they are also increasingly designing products to improve energy efficiency in the industries that they serve.

As well as mobile company Vodafone, the international environmental organisation gave its most favourable ratings to Silicon Valley stalwarts Cisco Systems and Google as well as to Swedish mobile vendor Ericcson and Japanese hardware company Fujitsu.

Cisco earned praise largely for its EnergyWise software, which manages energy consumption of connected devices. Google led the pack in use of renewable energy to power its server farms.

The recent trend toward cloud computing has led to spikes in the technology industry's power usage and Greenpeace said much of that power still comes from dirty sources like coal and diesel. The organisation is pushing the industry to offset the resulting carbon emissions by using renewable energy.

The report also notes that the technology sector in the States has backed away from earlier efforts to lobby for cleaner energy nationally.

Technology companies "aren't weighing in," said Gary Cook, Greenpeace's IT analyst. "They're leaving debates to the traditional energy companies, who are very happy with the status quo. But that's not in the IT sector's interest. It has a lot of money that could be made with a transition to a more efficient economy."

One notable exception is the Japanese mobile company Softbank, whose CEO called for Japan to move to renewable sources of energy after the Fukushima nuclear disaster in April.