. >> reporter: but mike berners lee who has written on the cost of everything says it's not that simple>> on the other hand, if you're home with the heating on which otherwise wouldn't have to be, that's not so good, and probably using more computing stuff than you would be. >> reporter: think about it, every email we send not only requires electricity to write, as it travels across the internet it gets stored and transferred from one mega server to another, gobbling up energy along the way, then if it gets read, it sucks up even more power. email may use 5% of the power needed to send a paper letter but we send and receive gazillions of them. done the math, would be taking 350,000 cars off the road. the principle is accurate. i.t. is a huge consumer of power and it's growing exponentially. many more people are receiving emails, and are streaming. if the cloud gets that much bigger and requires that much more storage, isn't that creating an energy-hungry infrastructure? >> it is, and we estimate that the information technology is probably responsible for 2% to 4% of the whole world's ca