Power over the elements is power over creation itself.[1]
Healing Wave is the first healing spell that a Shaman starts with. It is a shaman's most powerful single-target heal, and in most cases, it is also the most mana efficient.
Healing Wave is the biggest heal in the shaman's arsenal, and also the most mana efficient single target heal. The long casting time makes it somewhat unwieldy to use, but it provides a very large amount of instant healing when used in combination with [Nature's Swiftness] or [Maelstrom Weapon].
The casting time of Healing Wave starts out at 1.5 seconds and then increases with each rank up to level 18, where it reaches the final casting time of 3.0 seconds. At level 20, the spell is complemented by [Lesser Healing Wave], which has a 1.5 second casting time regardless of rank.
The large amount healed and the relatively slow casting time means that it is often useful to begin casting Healing Wave on a target that is taking damage before the target needs the full amount of healing done as the target will continue to take damage while you cast the spell. It can even be situationally useful to begin casting the spell on a target that has not yet taken any damage if you expect them to take a lot of damage during the next few seconds. If the heal turns out to be unnecessary, you can simply stopcast the spell before it finishes.
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Patch 4.0.1 (2010-10-12): Level requirement is 7, and the spell is no longer free, available after character creation. 
Hotfix (2009-04-22): "The Thunderfall Totem will no longer increase the casting time of Healing Wave or Lesser Healing Wave when Tidal Waves is active. [2]" 
Bornakk 2009-04-17. Recent In-Game Fixes - 4/16/09. Archived from the original on 2009-04-17. Retrieved on 2009-05-25.
