The modern cellphone user is highly attuned to energy usage. I assiduously monitor my phone's battery, tracking its decline from morning to evening, and then its return to fullness. There are even special "advanced power strips" that help people save energy while charging their devices.
The real energy cost to the world of an iPhone 6 is not charging its battery, though—it is creating the phone. Energy scholars call this embodied energy emergy, which is a terrible world for an interesting concept. The stuff that we own contains the ghost energy of all the production processes that went into making it.
And it takes a lot of energy to mine, refine, grow, and create materials. For a smartphone, researchers estimate that it takes roughly 1 gigajoule to create a modern smartphone. That's roughly 278 kilowatt hours, or 73 times the electricity used to charge the thing for a year.
Think about the difference of energy that's expressed here. If you're trying to reduce your personal energy consumption, does buying a smart power strip make sense? Or should you just keep your phone for an extra few weeks?