Eagerly awaited national energy efficiency standards for the little black boxes on the cords that connect many of our electronics--such as smartphones, computer laptops and electric toothbrushes--to wall outlets take effect this week. Known as external power supplies, or the less elegant term 'wall warts,' these power adapters may be small, but they consume a lot of energy. With 5 to 10 external power supplies in the average U.S. household, the new efficiency standards are projected to save consumers $300 million a year in electricity costs and reduce the carbon pollution that fuels dangerous climate change. The U.S. Department of Energy (DOE) projects that the new standards for external power supplies alone will cut nearly 47 million metric tons of carbon dioxide over 30 years, equivalent to the annual electricity use of 6.5 million homes.