The mana Innervate saves the target is significant, especially since the spell's cooldown timer is only 3 minutes. It is beneficial to any mana user. The short cooldown means that if you do not need it, you can cast it on another mana user in your group and have it ready again in a short amount of time. Saving Innervate for more than three minutes means you wasted a very large amount of potential mana.
It is a great solo tool - it lowers downtime by replacing a drink, or it can give extra free spells in a tough situation.
In five-player instances, it can be a good idea to save Innervate exclusively for the healer when they are low on mana. When playing as the healer, do not hesitate to Innervate early and often. Just make sure to save it when nearing a boss fight where you think you might need it.
In Hearthstone
This section contains information exclusive to Hearthstone and is considered non-canon.
Innervate is a basic Druid spell in Hearthstone. The flavor text reads: "Some druids still have flashbacks from strangers yelling "Innervate me!!" at them."
Notes
Innervate's buff is a Magic effect, so it can be dispelled; hence, you should be careful when using it during PvP.
Patch 10.0.0 (2022-10-25): Now a row 9 class talent (was a level 42 Balance and Restoration ability). Rank 2 converted into the [Natural Wisdom] talent.
Patch 9.0.2 (2020-11-17): Rank 2 added at level 54: If you cast Innervate on somebody else, you gain its effect at 50% effectiveness.
Patch 9.0.1 (2020-10-13): Duration has been reduced to 10 seconds and it no longer has a global cooldown. Now learned at level 42 (was 50).
Patch 8.1.5 (2019-03-12): Fixed a bug that caused Innervate to affect abilities that use resources other than mana.
Patch 7.0.3 (2016-07-19): Re-added at level 50 for Balance and Restoration (was level 54 for all druids) and redesigned. Now allows a friendly target to cast spells without spending mana for 10 seconds.
Old: Causes the target to regenerate mana equal to 50% of the caster's Spirit (excluding short-duration Spirit bonuses) every 1 sec for 10 sec. Total mana gained will never be less than 8% of caster's maximum mana.
Patch 5.4.0 (2013-09-10): Now restores mana based on the Druid's Spirit.
Patch 5.0.4 (2012-08-28): Now causes the target to regenerate 10% of the caster's mana instead of 5% of the target's mana. Additional self mana regeneration reduced from 15% to 10%. Now learned at level 54 (was 28).
Patch 4.2.0 (2011-06-28): Now grants an ally target 5% of his or her maximum mana over 10 seconds, but still grants 20% of the druid's maximum mana over 10 seconds when self-cast.
Patch 4.0.1 (2010-10-12): Now regenerates mana equal to 20% of maximum mana(was 225% of the base mana) Now learned at level 28 (was 40).
Patch 3.2.0 (2009-08-04): Duration reduced to 10 seconds, and cooldown reduced to 3 minutes. This means each use of Innervate will give half as much mana as before, but it will be available twice as often.
Hotfix (2009-05-19):Now properly restores the correct amount of mana to Shapeshifted targets that do not have a mana bar active.
Patch 3.1.2 (2009-05-19): This ability has been redesigned to grant 450% of the casting Druid's base mana pool to the target over 20 seconds.
Previously based on spirit.
Patch 3.1.0 (2009-04-14): This spell no longer costs mana.
Patch 2.0.1 (2006-12-05): Innervate moved to the Balance tree, making it castable while in Moonkin Form.
Patch 1.11.0 (2006-06-19): This spell is now a base ability for all Druids, trainable at level 40. Any Druid who formerly had the Innervate talent now has the Swiftmend talent instead.
Previously the 31 point talent in the Restoration tree.
[Innervate].
[Mass Entanglement]/
[Ursol's Vortex]
Patch 10.0.5 (2023-01-24): Can now be cast in 
[Bear Form]. 
Patch 9.0.2 (2020-11-17): Rank 2 added at level 54: If you cast Innervate on somebody else, you gain its effect at 50% effectiveness. 
Patch 8.1.5 (2019-03-12): Fixed a bug that caused Innervate to affect abilities that use resources other than mana. 
Patch 7.0.3 (2016-07-19): Re-added at level 50 for Balance and Restoration (was level 54 for all druids) and redesigned. Now allows a friendly target to cast spells without spending mana for 10 seconds.
Patch 6.0.2 (2014-10-14): Removed. 
Patch 5.4.0 (2013-09-10): Now restores mana based on the Druid's Spirit. 
Patch 4.2.0 (2011-06-28): Now grants an ally target 5% of his or her maximum mana over 10 seconds, but still grants 20% of the druid's maximum mana over 10 seconds when self-cast. 
Patch 3.2.0 (2009-08-04): Duration reduced to 10 seconds, and cooldown reduced to 3 minutes. This means each use of Innervate will give half as much mana as before, but it will be available twice as often. 
Patch 2.0.1 (2006-12-05): Innervate moved to the Balance tree, making it castable while in Moonkin Form. 
Patch 1.11.0 (2006-06-19): This spell is now a base ability for all Druids, trainable at level 40. Any Druid who formerly had the Innervate talent now has the Swiftmend talent instead.
