The new rating system is a cellphone industry response to heavy criticism from environmentalists. The industry has become the world's top consumer electronics business by volume.
The new ratings system covers all chargers currently sold by Nokia, Samsung, Sony Ericsson, Motorola and LG Electronics, and ranges from five stars for the most efficient chargers down to zero stars for the ones consuming the most energy.
If left plugged into the socket, chargers continue to use electricity even if the phone is disconnected. Nokia said around two-thirds of the electricity used by mobile phones is wasted this way.
"If the more than 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," Nokia said in a statement.
The world's top four charger makers include Flextronics, China's BYD Co, Emerson Group and Finnish Salcomp.
"This should be positive for us," Salcomp Chief Executive Markku Hangasjarvi told Reuters. "Such chargers are more difficult to produce, their average selling price is higher and they demand special know-how."