This article became obsolete as of Patch 2.4. For Spirit and MP5 comparisons relevant as of 2.4, please see 2.4 Mana Regen - Part 1: The Basics and 2.4 Mana Regen - Part 2: The Mana Regen Calculator.
Within each class, the playerbase debates different game mechanics. Rogues debate Mutilate vs. Hemorrhage. Mages debate Fire vs. Arcane. Warlocks argue about whether they'd like their Fel Fire of Ultimate Win to be green or red. And for Restoration Druids, we frequently argue about the value of Spirit relative to MP5.
According to WoWWiki's calculations Blizzard considers 1 mana per 5 equal in value to 2.5 Spirit. That means, for the same item budget, you could get 100 MP5 or 250 Spirit. Which would you rather have? Let's look at each stat individually to shore up your rationale (whatever it might be).
What Spirit Does
From the official site, Spirit is described as the stat that:
Increases Health regeneration rates out of combat and Mana regeneration rates when not casting spells.
Sounds pretty good. More mana means more healing, right? Sort of. Not all classes benefit from Spirit in the same way. Some classes benefit more than we do from Spirit (like the Priest - boo! hiss!) and some classes — such as the Warlock and Paladin — benefit far less (these classes are inferior and undeserving of our Innervate). Here's how it breaks down among the four healing classes:
| Class | Mana/Tick | MP5 per Spirit |
| Druid (Caster, Tree, Moonkin) | (SPI/4.5) + 15 | 0.555 |
| Druid (Kitty, Bear) | (SPI/5) + 15 | 0.5 |
| Paladin | (SPI/5) + 15 | 0.5 |
| Priest | (SPI/4) + 12.5 | 0.625 |
| Shaman | (SPI/5) + 17 | 0.5 |
As you can see, Priests regenerate the most mana for each point of Spirit, followed by Druids, followed by everyone else (including us when we shift into a Feral form). Interestingly, a Druid with the Living Spirit talent has mana regeneration per point of Spirit higher than that of Priests:
| Class | Mana/Tick | MP5 per Spirit |
| Druid (Caster, Tree, Moonkin) | (SPI/4.5) + 15 | 0.555 |
| Druid with Living Spirit | ((1.15 * SPI)/4.5) + 15 | 0.639 |
| Priest | (SPI/4) + 12.5 | 0.625 |
Spirit and the Five Second Rule
One of the biggest limitations of Spirit is that you only receive the benefit of its mana regeneration if you haven't cast a spell within the last 5 seconds. This is known as the "5-Second Rule" (5SR):
After a character expends mana in casting a spell, the effective amount of mana gained per tick from spirit-based regeneration becomes a ratio of the [the values listed above], for a period of 5 seconds.
The default percentage of mana regeneration within the 5SR is 0%. However, there are several talents and abilities that boost this value, including Priest Meditation and the Druid-equivalent Intensity. Both of these are 3-point talents that afford an additional 30% of mana regeneration "while casting" (i.e., inside the 5SR). Having three points in Intensity is a prerequisite for Nature's Swiftness so it's unlikely to find a Restoration Druid without it.
| Class | Mana/Tick |
| Druid with Intensity | 0.3 * ((SPI/4.5) + 15) |
| Druid with Intensity and Living Spirit |
0.3 * (((1.15* SPI)/4.5) + 15) |
There are also a few items which can boost your mana regeneration while casting, at least temporarily. Perhaps the most notable is the Bangle of Endless Blessings which has a chance to proc an additional 15% mana regeneration while casting for 15 seconds (at level 70):
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Of course, you already have one of these after reading the article on Getting the Most out of Innervate, right? And speaking of Innervate it's worth noting that since Innervate is based upon its recipients base mana regeneration (outside of the 5SR), the more Spirit the better. This also means that giving your Innervate to a Warlock is less efficient than to a Priest or another Druid (or to yourself).
For more information on mana regeneration and the 5 Second Rule, be sure to visit Egotistical Priest and Priestly Endeavors.
The Tree of Life Aura
With the release of the Burning Crusade (technically just before), Blizzard added new talents for all classes, among them the 41-point Restoration talent, Tree of Life:
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While in Tree of Life, a Druid causes all heal spells cast upon her party members to receive 0.25 points of +Healing for each point of Spirit she has. At 400 Spirit, that's 100 +Healing (115 with Living Spirit). (For more information about how the +Healing coefficient affects our spells, see Mystery No More: +Healing Explained.) In a 5-man instance, that's effectively 100-115 extra +Healing for the Druid since she won't be healing anyone outside of her party. In raids, this healing bonus generally only benefits one or more main tanks, assuming the Tree has been placed in the MT group and the dynamics of a given encounter allow for the form to be used.
Mana per Five Seconds (MP5)
This term is pretty self explanatory as how many points of mana you will regenerate within five seconds (2.5 ticks). While it's often used as an overall measure of a character's ability to regenerate mana, both in and outside of the Five Second Rule, it's also available as a pure statistic on many pieces of gear. Unlike Spirit, MP5 runs all the time, disregarding the 5SR altogether. Acquiring a new item that grants you 4 more MP5 than you had before will therefore increase your mana regeneration while casting and while not by 4. There isn't much more to describe about MP5 since it's a pretty straightforward stat.
Spirit vs. MP5
According to WoWWiki.com, each point of MP5 is valued equal to 2.5 points of SPI. How much each is actually worth to you personally, however, depends on how much time you spend inside the 5SR. The more time spent outside the 5SR, the more beneficial Spirit is. More time spent "casting" increases the value of MP5 relative to Spirit. A good way to determine how much time you spend inside the 5SR is to run a UI addon like RegenFu (Ace2, FuBar required), which not only summarizes the amount of time spent inside the 5SR by each fight, but also calculates the relative value of Spirit to MP5 for that specific encounter. It is a more significant relative measure on boss fights than for trash when raiding since it's more rare to run out of mana on trash.
Sample Data from RegenFu
WoWWiki.com includes an incredibly useful article on Mana Regeneration formulas (albeit, based upon Priests) that we can adapt to determining the relative values of MP5 and Spirit for Druids. Adjusting the formula to account for Druids' slightly lower base mana regen:
Spirit required to match 1 MP5 =
Applying the above formula, we can derive a graph of the amount of Spirit required to equal MP5 based upon the amount of time spent within the Five Second Rule, both with and without Innervate*. Rather than only evaluating mana regeneration from Spirit at the new 30% Intensity, I also calculated it at the previous 15% for comparison's sake. Once again, I've graphed it over the % time spent within the Five Second Rule and according to the use of the following talents and abilities:
- Intensity (both 2.2 and 2.3 versions)
- Innervate
- Living Spirit
- Possible combinations of the above
Here's the graph of the new Intensity vs. the old Intensity. Future values are shown in a darker shade of the plots of their current values (eg. Red for "2.3 Living Spirit + Innervate", pink for the current value.
From this graph, note the following:
- With 2.2 Intensity, you would need to be inside the 5SR (considered casting) no more than 32.5% of the time for the value of Spirit relative to MP5 to match that which is currently budgeted by Blizzard. With 2.3 Intensity, that number is increased to 40%. With Living Spirit, the number increases from 45% to 53%. With Intensity and Innervate, the number increases from 62.5% to 78%. With Living Spirit, Intensity, and Innervate, the number goes from 75% to 92.5%.
- Assuming a Druid has both Intensity and is using her Innervate at every opportunity, the changes to Intensity with Patch 2.3 will make the value of Spirit much more closely match that currently being assigned in Item Values, especially if she is able to remain outside the 5SR 22% or more of the time.
- Even if you were always within the 5SR (Lifebloom maintenance) and assuming you are using Innervate at every opportunity, 1 MP5 will be approximately worth 3.1 Spirit (down from 4.3 prior to Patch 2.3). With Living Spirit, 1MP5 is worth approximately 2.8 Spirit (down from 3.7 prior to Patch 2.3). That's an increase of value in Spirit by 28%, 24% if you factor in Living Spirit (the additional mana regenerated with Living Spirit is outweighed by the mana regenerated by Innervate so even though you will get a substantial increase, the rate of increase is not as high).
Factoring in Blessing of Kings
By popular request, I've added a graph that compares the valuation of Spirit relative to MP5 with Blessing of Kings, using the 2.3 value for Intensity (30% mana regeneration while casting). Non-BoK values are graphed in a lighter color than their BoK values and, as one might expect, the 1.1 factor on total Spirit causes each plot to shift slightly down:
Delos of Cenarion Circle has a new Balance blog (Ba-log?) that embraces my most beloved of Moonkin monikers, 
These changes are an indirect buff to Druids, or at least to our 6-second crowd control ability, Cyclone. Because while the potency of Warlock Fear, Mage Polymorph, Hunter Freezing Trap, and Rogue Sap was reduced by 17%, our 6-second Cyclone remains untouched. In a manner of speaking, Cyclone is getting buffed 20% relative to the adjusted forms of crowd control.* Of course, our Entanging Roots ability is one of the forms of crowd control whose duration is being reduced, but Roots seldomly lasts its full duration anyway.
Am I the only Durid (the Druid equivalent of “Huntard”) who hasn’t figured out how to make this work, yet? I once tried this in a 5v5 and watched helplessly as my four teammates were turned into so much guildmate-flavored paste. And were subsequently eaten by the 5-year old playing a Warlock on the opposing team. He was alone, too.
