AT&T has announced that its hoping to step into Buffy's shoes and rid the world of vampires. Just as the undead feast on the life-force of unsuspecting victims, mobile phone chargers can continue to suck power from the mains even when disconnected from the device and left in the wall socket. With the forthcoming release of the ZERO charger, AT&T is aiming to change that.

As its name might suggest, the ZERO charger from AT&T and Superior Communications automatically shuts down when it's no longer needed, putting an end to "vampire draw" that can suck out "as much as 5 to 20 times more energy than stored in the battery", enough wasted energy to "power 24,000 homes for a year, or brew three to four million cups of coffee each day" according to calculations made by the company.

The communications giant estimates that around 277 million wireless device users charge their device at least three or four times per week for around eight hours. Around 80 percent of those users are thought to leave the charger plugged in even when the battery is fully charged and the device disconnected which can continue to draw 170mW when idle and, according to AT&T, accounts for around 12 percent of the annual electricity usage in the U.S.

The ZERO charger will be available in AT&T stores throughout the U.S. or online from May for about the same price as other chargers and is said to improve on charging efficiency as well as not wasting power when it detects that it is no longer connected to a device.

USB "block and cable" connectivity ensures multiple device current and future compatibility and could lead to a cut in the number of chargers produced (which will result in less of a land-fill problem). Its eco-friendly credentials continue by being encased in recycled packaging.