Mark Mills, CEO of Digital Power, penned a report with the catchy title "The Cloud Begins With Coal". After adding up all the numbers and dividing by his shoe size, Mills has calculated that an average iPhone uses about 361 kilowatt-hours each year after factoring in wireless connections, data usage and battery charging.
By comparison, a medium sized refrigerator with an Energy Star rating only uses about 322 KWh a year.
While smartphones and tablets require very little energy to charge, the true culprits aren't the devices, but the stuff running in the background that supports wireless connections that are always on.
To run an iPhone there are servers that run 24 hours a day, seven days a week. These need air conditioning, manufacturing centers to build the devices, and nonstop electricity to power broadband networks.
The global ICT ecosystem uses 1,500 terawatt-hours of power every year. This is equal to the total electricity generated by Japan and Germany combined, and as much electricity used to light up the entire world in 1985. ICT consumes about 10 percent of all electricity generated in the world, Mills wrote.
Humanity is moving to a world where each house has a refrigerator and owns several smartphones. To make matters worse mobile internet and cloud computing require more energy than wired networks, he added.
Mills thinks that the world will need a lot more electricity in the future.
All of this adds to a carbon footprint that continues to grow in size, and coal is still the largest source of electricity in the US - with carbon producing coal plants stuffing up the world's ecosystem.