Reduces the mana cost of your damaging offensive spells by X%.
Convection is a passive talent that reduces the mana cost of a shaman's damage offensive spells.
% Mana Reduction
It is most worthy of consideration for Shamans who use these spells often, and compared to Concussion would be preferred if the Shaman is concerned about running out of mana during battle. It is strongest to a Shaman investing further in the Elemental tree, and Shamans who are devoted to destruction might consider getting both Convection and Concussion.
PvP Shaman would probably be better off saving the 2 points for something else. Most PvP fights don't last long enough for the reduced mana costs to have any real affect. PvE Shaman however should consider taking both Convection AND Concussion as there can be some hard burns which can deplete your mana quickly.