Pike predicted that much of the processing being handled by today's data centres will have been transferred to the Cloud by 2020.

"The growth of Cloud computing will have a very significant positive effect on data centre energy consumption," senior analyst at Pike, Eric Woods, says.

"Few, if any, clean technologies have the capability to reduce energy expenditures and greenhouse gas production with so little business disruption. Software-as-a-service, infrastructure-as-a-service, and platform-as-a-service are all inherently more efficient models than conventional alternatives, and their adoption will be one of the largest contributing factors to the 'greening' of enterprise IT."

Which brings us back to Jevons.

The problem is the debate focuses on two sides that are talking about the same issue, but not on the same issue. There is no doubting Cloud's efficiency.