That's because the moment someone uses a phone (or a tablet, laptop or other computer) to access the internet they are also using the servers that are used to store and move data. "It's not that particular mobile phone models aren't energy efficient, it's that we use these devices to access cloud computing services, and this always-on IT culture requires huge data farms to be located around the country," said Peter Hopton, the founder of Iceotope, a green IT business that cools servers using liquid rather than air conditioning.
Here's Mills' analogy: "When you go and sit in your car and turn it on you are just using the energy in your gas tank. But when you use your smartphone you are connecting to computers all around the world and turning them on too. It's as if turning on your car turned on all the other cars in the car park as well."
The UK has the greatest concentration of data farms in the world, Hopton said, with a single server in a typical data centre creating the same carbon footprint each year as a Range Rover sport. Globally, the world's computing economy uses more energy each year than aviation.