Ask Focus on Energy

These are external plugs you use to power electronics.

External power adapters, also known as power supplies, are crucial to the operation of virtually all small electronic devices. As many as 1.5 billion are in use in the U.S. — that's about five for every person. The total electricity flowing through all types of power supplies is about:

• 300 billion kWh/year, and
• 11% of the national electric bill

They convert high voltage AC electricity from the wall outlet to the low voltage dc power used to power electronic products, like MP3 players, personal digital assistants, camcorders, digital cameras, laptops and cordless and mobile phones.