“The annual cost to charge an iPad is just $1.36, according to the Electric Power Research Institute, a non-profit research and development group funded by electric utilities.
By comparison, a 60-watt compact fluorescent bulb costs $1.61, a desktop PC adds up to $28.21 and a refrigerator runs you $65.72 in the U.S.
….
But if people are using iPads instead of televisions to play video games, or ditching their desktop computers for iPads, the shift to tablets could mean lower overall power consumption. A desktop computer uses 20 times more power than an iPad. 
….
Residential power demand is on track to fall for the third straight year, according to the government. A weak economy is keeping people in smaller houses and shacked up with others. At the same time, efficiency programs are pushing more efficient light bulbs, air conditioners and other devices into homes. Refrigerators use a quarter of the power they used a generation ago, according to EPRI. 

But there’s an even cheaper way to go than the iPad. EPRI calculated the cost of power needed to fuel an iPhone 4 for year: just 38 cents.”

http://phys.org/news/2012-06-ipad-year.html 

About 11% of our residential electricity goes to lighting.  Moving to more efficient lightbulbs will cut the power used for lighting by a factor of four or more.