- Not available on that edition (the reason is in the tooltip)
- Depends on the setting, your class or another addon (details in the tooltip)
What it does
Checks how much of its main power, such as rage, energy or mana, the unit specified has as a percentage of its maximum, compared with the percentage you set.
Why you might use it
Compare a unit's primary power as a percentage of its maximum, which keeps working when talents or gear raise the cap. Use it to spend energy or focus before it caps (above 90%), or to hold a Warrior's rage dump until rage is high. Not available on Retail or Forever, where the game hides these values from addons. See also Power and Mana Percentage.
Example
your power is greater than 90%
Settings
What each setting in the condition editor means, from the game's own help.
Unit - The unit this condition uses as the target of comparison.
Operator - How to compare Power with the Power value. This comparison uses basic mathematical comparison operations.
Power - The power value of Unit as a percentage of their total power. Power is a statistic that is class (and sometimes spec or form) specific (eg. Warriors have Rage.)