Efficiency

Efficiency is defined as "the ratio of the effective or useful output to the total input in any system" or, more colloquially, as "getting the most bang for your buck". In World of Warcraft, nearly every viable strategy is based on some kind of efficiency, generally minimizing or maximizing some value or concept. This makes efficiency complicated as a topic, however, because any given process can be optimized more than one way. What is efficient in one sense may not be efficient in another.

There are many ways to be efficient in World of Warcraft; however when most people mention "efficiency", usually they mean efficiency in one of the following (related) ways:


 * Mana efficiency (that is, net effect achieved (usually damage or healing) for a given expenditure of mana)
 * Minimizing downtime (that is, behavior that allows you to continue to act without stopping to rest or divert)

Other effects, such as maximizing the damage you do per second, while technically a form of efficiency, tend to be referred to as "maximizing" or "optimizing".

Minimizing downtime
Downtime is thought to be the enemy of grinding. The less you have to travel or stop to eat or drink, the more you can focus on getting experience. Minimizing downtime is usually equivalent to maximizing XP per second (or, more realistically, XP per minute). Some general tips on this:


 * Grind in places where the mobs tend to be near to each other (to minimize travel time) and respawn quickly (to minimize waiting).
 * Healers should use bandages to heal.
 * If questing, try to deal with all of the quests in a specific area at once (to minimize travel time).
 * Consider that downtime also includes skill- and profession-leveling or time needed to fill other goals. Look for ways to combine short-term goals (e.g. maximizing XP/second) with long-term goals.  For example, if you are a tailor, you might consider grinding mobs that drop cloth to be overall more efficient than grinding those that don't, even if the cloth-droppers provided slightly less XP/second.

Mana efficiency when healing
A subset of mana efficiency is healing efficiency, and this is arguably the area where efficiency is the most important. If a healer is not mana efficient, he or she is likely to run out of mana before the fight is over and be unable to continue healing, likely resulting is player deaths and potentially wipes. With the large number of healing spells, gear, buffs, and talents that manipulate the math involved, it can be difficult to determine which heals are the most efficient. Further, there are multiple ways in which healing can be thought of as efficient. The two that tend to matter most are hit points healed per point of mana (HPM) and hit points healed per second (HPS).

Generally speaking, slower healing effects tend to cost less mana per point healed while faster spells such as Flash Heal and Lesser Healing Wave are less efficient, though this is not always the case (Flash of Light being a notable exception). Spell power from gear serves to make things even more complicated, as some spells scale better than others with spell powers. For example, the druid spell Rejuvenation is relatively weak without any spell power, but scales to become one of the most mana efficient single-target healing spells in the game as spell power increases. As a general rule, however, spells which heal a lot per second (high HPS) will have fairly poor mana efficiency (low HPM) and vice versa.

Fortunately, there are web sites that allow you to play with all of these values. Having a rough idea of the relative HPM and HPS of your healing spells is vital to doing a good job as a healer, as frequent use of low-HPM spells in the wrong situations will drain your mana, while using low-HPS spells in emergencies will lead to deaths. Many times, the differences between different healing spells can be summed up in terms of HPM and HPS.

Mana efficiency when dealing damage
Determining the method that delivers the most damage per point of mana spent depends highly on class. Gear and talents also matter a great deal. The formulas used in determining damage are varied, and can be manipulated in many ways. See spell damage comparison for more information.