Software engineer Ken Shirriff took a close look at 12 different USB power adapters and confirmed what we already suspected -- that counterfeit chargers are junk. They are poorly constructed and can cause serious damage to both your devices and yourself.
Shirriff measured the performance of a variety of branded chargers including those from Apple, Samsung, Motorola, Belkin, Monoprice and more. He also threw in a few counterfeit power adapters for the iPhone and iPad. While Apple's official chargers scored well in the tests, the counterfeit ones scored poorly. Not only do the counterfeit adapters deliver significantly less power than advertised, the chargers also ignore basic safety standards. Shirriff says "you're putting your phone, and more importantly yourself, at risk if you use one of these chargers."
Shirriff gives tips on spotting these fake adapters, but notes that they are often so similar to Apple's chargers that it is difficult to tell them apart. Your best (and safest) bet is to cough up the $29 for an Apple power adapter and rest easy knowing that you are getting a quality charger that won't burn your house down.
You can read Shiriff's full performance report that covers both the branded and counterfeit chargers on his website.