Nokia, LG, Samsung, Motorola, and Sony Ericsson have launched an energy rating system for mobile phone chargers in an effort to make the industry more 'green'.

The five manufacturers have joined forces to help armchair eco-warriors determine whether their mobile phone is a bastion of energy efficiency or a fat leech feasting on the world’s power supply.

The ratings will adhere to the European Commission's energy standards but will only reflect the amount of energy consumed when the charger is idle (i.e. the charger is still plugged into the wall socket but it has been disconnected from the phone).

The no-load power consumption score chart has five stars representing devices that use less than 0.03w per hour (5-stars) to those that use more than 0.50w (0 stars).

Mobile phones are ubiquitous in the modern world. Nokia scientists claim that, of the 6.72 billion people on the planet, at least half of them own a mobile phone. It doesn’t take a genius to work out that the amount of energy consumed annually by billions of idle chargers would exceed that used by a small city.

A Nokia press release explains: “If the three billion people owning mobile devices today switched to a four or five star charger, this could save the same amount of energy each year as produced by two medium sized power plants.”

Of course, chargers only consume energy when they are plugged in. Thus, if you want to help the environment without having to shell out for a new charger, just unplug your existing one and put it back in its box. It's easy.