The above picture shows the twelve chargers I analyzed. The charger in the upper-left is the cube-shaped Apple iPhone charger. Next is an oblong Samsung adapter and a cube Samsung adapter. The Apple iPad power adapter is substantially larger than the iPhone charger but provides twice the power. The HP TouchPad power charger has an unusual cylindrical shape. Next is a counterfeit iPhone charger, which appears identical to the real thing but only costs a couple dollars. In the upper right, the Monoprice iPhone charger has a 30-pin dock connector, not USB. The colorful orange charger is a counterfeit of the Apple UK iPhone charger. Next is a counterfeit iPad charger that looks just like the real one. The Belkin power adapter is oval shaped. The KMS power supply provides four USB ports. The final charger is a Motorola Charger. Summary of ratings The chargers are rated from 1 to 5 energy bolts, with 5 bolts the best. The overall rating below is the average of the ratings in nine different categories, based on my measurements of efficiency, power stability, power quality, and power output. The quick summary is that phone manufacturers provide pretty good chargers, the aftermarket chargers are worse, and $2 counterfeit chargers are pretty much junk. Much to my surprise, the HP TouchPad charger (which isn't sold any more) turned out to have the best overall score. The counterfeit iPhone charger set a new low for bad quality, strikingly worse than the other two counterfeits.
ModelOverall rating Apple iPhone Apple A1265 Samsung oblong Samsung travel adapter ETA0U60JBE Samsung cube Samsung travel adapter ETA0U80JBE Apple iPad Apple 10W USB Power Adapter A1357 HP TouchPad Hewlett Packard LPS AC/DC Adaptor P/N 157-10157-00 Counterfeit iPhone Fake Apple A1265 "Designed by California" Monoprice Monoprice Switching Mode Power Supply MIPTC1A Counterfeit UK Fake Apple A1299 Counterfeit iPad Fake Apple 10W USB Power Adapter A1357 Belkin Belkin UTC001 KMS KMS-AC09 Motorola Motorola AC Power Supply DC4050US0301 Inside a charger These chargers cram a lot of complex circuitry into a small package, as you can see from the iPhone charger below. (See my iPhone charger teardown for more details.) The small size makes it challenging to make an efficient, high-quality charger, while the commoditization of chargers and the demand for low prices pressure manufacturers to make the circuit as simple as possible and exclude expensive components, even if the power quality is worse. The result is a wide variation in the quality of the chargers, most of which is invisible to the user, who may believe "a charger is a charger".