Deciphering the Power Label On Your A/C Adapters

Deciphering the Power Label On Your A/C Adapters

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Chris Perez
Apr 2, 2012

Turn over the charger or plug to any electronic device and you'll notice small print and symbols related to the power requirements of your device. But what do all those symbols all mean and why do they matter when plugging in...

Here's what a typical battery charger or A/C Adapter looks like underneath it. A cryptic, oft misunderstood label...

Let's look at some of these terms individually and talk about what they might mean to you.

The Power Numbers
Wattage
This is often the first marking you might find on your A/C Adapter. It simply notes the power of the adapter. You may notice the iPhone power adapter is rated only for 5W, while your iPad power adapter will have a 10W rating. Thus, a 5W adapter won't have enough power to charge an iPad effectively. However, a 10W adapter can be used to charge an iPhone. Typically a device just gathers the power it needs, so a 10W adapter doesn't mean twice the charging speed.

Input Voltage
The next item you might see is a reference to the input voltage. The input voltage is the voltage the charger is rated to handle when plugged into an outlet at our homes, cars, etc. Here in the US our homes and buildings are wired with 100V, while European countries use 200-240V. Plugging a product rated at lower voltage (like a US hair dryer) into an outlet of higher voltage (European outlet) will be damaging and could even cause sparks or fire. Watch out!

Conversely, plugging a higher rated (European device) into a lower rated outlet (US) will not give the device enough power to work properly. In both cases an adapter will be required to tune-down or ramp-up the voltage as necessary.

Input Amps
This is a measurement of the electric current given to the device. The ~ symbol notes that the device is taking in an alternating current (A/C), the type of power that lives in the walls of our home. The power alternates polarity at a given frequency.

Hertz
The frequency of the alternating current above is measured in Hertz (Hz). A measure of how many times per second the signal shifts polarity. In US structures, a rate of 50Hz is the norm while in Europe a rate of 60Hz is used. Its common for adapter to handle both frequencies, but check your label for certainty if traveling abroad.

You may have also seen the 'GHz' moniker attached at the end of desktop computers you purchase. The 'G' stands for Giga, and is scientific shorthand for 1 million. In those situations the label is denoting how fast instructions are fetched by the computer's internal processor. A higher number for a similarly constructed processor (single, dual-core, quad-core) is better.

Output Voltage and Amps
Next to the output you'll likely see two lines, a solid on top and a dashed line below. This is the symbol for direct current. The charger is basically taking the alternating current from your home and converting it into a direct current ideal for our electronics. This symbol is followed by a voltage and amp spec. Engineers might recognize that the voltage x amps number will give you the total wattage of the charger or adapter. Again, these numbers are indicating the rate at which power is sent from the outlet to your electrical device.

Miscellaneous Symbols and Markings

What looks like a recycle bin with an X through it, is the symbol for WEEE — Waste Electrical and Electronic Equipment. This is an initiative in the European Union that requires manufacturer's to provide a system through which electronic devices can be disposed of or recycled without cost to the consumer. The manufacturer does not have to necessarily implement this system for the US.

This symbol indicates the type of construction of the adapter or charger. Two squares indicates Class 2 construction, which means the device doesn't require a ground connection. This differs from a Class 1 device which does require a ground connection.


This symbol is called a C-tick. It is used to denote that the product is safe for sale in Australia.

Similar labels stating compliance with a specific countries testing requirements or standards can also be seen on the adapter or charger.



The CE Mark is a conformity symbol for European countries. The symbol stands for Conformité Européenne.






The UL is a certification mark of Underwriters Laboratories Inc. You may see a c on the left of the mark denoting compliance in Canada, as well as a us on the right indicating compliance for the US.





The TUV/GS symbol is a voluntary certification label recognized in Germany for safety-tested products.





There may be other symbols used for Japan and other countries but the ones above are the most common.

Bet you didn't think you could find all that information from the back of a power label now, did you?

(Images: Chris Perez)

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