[glogla]

Back of the napkin: hundred million iPhones recharging their 13 Wh battery once a day every day from zero to full for a year is about 60 % the electric energy that this power plant [1] makes in a year.

Not huge amount of energy, but not negligible either.

[1]: https://en.wikipedia.org/wiki/Agua_Caliente_Solar_Project

edit: I see someone else did the math as well.

[datadrivenangel]

Not negligible, but also a small cost of the total cost of the iPhone system. call it 500 megawatts for 100m iPhones, which for moderately expensive generation capacity is ~ 2million per megawatt of capacity, works out to $10 per phone in electricity. A typical power plant has expected lifetimes of ~25-50 years, which if we assume a generous 5 year phone lifespan, and a 25 year plant life...

That works out to $2 per iPhone to build power plants to charge the iphone every day for it's an entire life. Not bad for a device that costs hundreds of dollars.