EPRI the Electric Power Research Institute issued a report on how much power an ipad uses in a year and how much it costs to power the ipad.
Only $1.36 per year for the 11.86 kilowatt hours a year the ipad needs. My friend Dr. P in Anaheim with his 100 miles a day commute in his Tesla that uses 40 kilowatt hours a day of AC electricity could power his ipad for more than 3 years with the power he uses in a single weekday going to and from work.
A Starbucks store has machines that make steam and espresso that use a lot of electricity. The stores also have lighting and air conditioning. In 2012 Starbucks stores used 6.36 kilowatt hours per square foot permonth. If the average store is 800 square feet, the average store will use 61,056 kilowatt hours per year and could power 5,148 iPads all year long.
I wrote about Starbucks in 2007 and Omninerd picked it up.
The iPad only uses 5% of the power of a desktop computer so my hat goes off to Apple for the ipad. Starbucks has a long way to go before becoming pale green.