Mana Efficiency

One of the biggest challenges for healers is maintaining our healing output without running out of mana. Obviously, using appropriate gear and consumables is one way to help ensure we don't zero out that precious blue bar, but that can only take us so far. Choosing the appropriate spell - both in terms of which spell to cast and which rank to use - is an equally important part of the equation.

In general, the choice of spell is fairly straightforward. If you're healing a single target exclusively, Healing Wave is your best bet. When charged with group/raid healing, Chain Heal really shines, especially with the Improved Chain Heal talent giving an extra 20% healing output. In terms of pure healing output per mana spent, Chain Heal is our most efficient spell (assuming an average of two players healed per cast), which is why shaman are at our best in a raid-healing role.

The other way to conserve your mana is by casting a lower-ranked version of your spells. Although there is a penalty to your +heal coefficient for using these spells, the lower mana cost outweighs the loss in raw healing for any reasonable +healing values. From a strict ratio of healing done per mana spent, the lowest ranked spells are almost always the most efficient (excluding Healing Wave 1-4 and Lesser Healing Wave 1, all of which have additional penalties to their spell coefficients). However, these lower ranked spells won't have the throughput to keep your teammates alive, so there's a delicate balance to be maintained.

• When healing a main tank, there are generally multiple healers assigned. To avoid overhealing and wasting mana (whether yours or other healers'), you should almost always down-rank your spellsIn these cases, your goal isn't to heal the tank to full health by yourself, but with the combined spells of all of the other healers. Depending on how many healers have been assigned to the tank and how much damage he or she is taking, I generally aim to heal about 2,000 health per non-crit casting (Rank 6 or 7 depending on your +healing stat). This greatly reduces my risk of overhealing (or causing others to overheal) while allowing me to conserve my mana. Of course, it's better to overheal than underheal, so if the tank spends too much time at anything other than full health, you should consider using a higher rank.
• Raid healing is a different animal altogether, but the basic principal is the same: Select the rank that provides enough healing to keep your teammates alive. Unlike healing a tank, you're not necessarily worried about keeping everyone at full health, but you're also less likely to have backup. There are significant improvements in Chain Heal's mana efficiency between Ranks 5 and 4, and Ranks 3 and 2 so I will typically choose from Ranks 2, 4 and 5 depending on the healing output requirement. When in doubt, start with Rank 4 and either move up to 5 if the healing is insufficient, or drop down to Rank 2 if you have too much overhealing.
• As a sidenote, don't be afraid to use Lesser Healing Wave if needed to keep someone in your care alive. The mana efficiency is poor, but that's not your goal in an emergency situation. I would recommend against down-ranking, however, as the lower ranks have only minimal gains in efficiency and if things are desperate enough to need LHW, you want maximum healing throughput.

Choosing which spells to use is part of the "art" of playing a healer. After a while, you'll be able to feel the flow of the battle well enough to instinctively up-rank or down-rank your spells, which will greatly improve your efficiency and effectiveness as a healer. If you're not yet to that stage, I've uploaded an Excel spreadsheet to File Front to help you along your way.

Good luck!