It's complicated;
In emps you have 1 game tick every 500ms (every half second). This means 2 ticks per second. Prayer points are a tenth of your level, this means a player with 99 prayer has 990 prayer points. This is for more accurate calculation.
In order to describe the effect of prayer equipment bonus on prayer points drain, i have to explain how the drain works first.
Depending on what prayer you are using, they are assigned a value that determines the timer on how fast it drains.
For example, by using piety, you have a drain value of 113 (the cheapest prayer being 10). This gets multiplied by 20 = 2260 when piety (so from 200-2260 if you only use 1 prayer at a time, multiple prayers stack)
Your base prayer bonus of 4500 + (your equipment bonus *75) determines the prayer bonus. The timer value of 2260 is substracted from this prayer bonus. (2240 if there is no prayer bonus).
Your prayer point drain is determined by dividing the tick of 500 by the remainder (2240), times 10 = 2.23
Every game tick your prayer points (NOT your level) is reduced by 2.23. This means that roughly you deplete 1 prayer level per 2 seconds by using just piety.
If you were wearing maxed out prayer equipment bonus, 60 in the example, you will double your base prayer bonus to 9000, you reduce your prayer points by 0.74 and thus deplete roughly 1 prayer level per 7 seconds instead of 2 when using piety.
conclusion: Wearing 60 prayer bonus instead of 0 prayer bonus effectively multiplies the time you can leave your piety on by 2.5. If you use more prayers, this multiplication is less, if you use less prayers this multiplication is more. Prayer equipment bonus has much more effect on your time remaining than using less or more prayers (!)
