Mercenary initially costs 0 PWR to use, and its cost increases by 2 PWR on each use, but is reset to a cost of 0 PWR each time the alarm level changes. This means in general its PWR cost is equal to 2 times the number of uses of Mercenary during the current alarm level. After alarm level 6, Mercenary's PWR cost continues to reset every 5 steps of the alarm tracker.
Mercenary's efficiency (in PWR cost per firewall hacked) depends on how frequently you use it. Mercenary will cost too much PWR to hack everything, but when you add another breaker program or Buster Chips, or use EMP Packs or Dr. Xu's Subdermal Tools instead of hacking some devices, Mercenary can be quite efficient — even when used a fourth time for a cost of 6 PWR, its average efficiency can still be better than Lockpick's.
|Uses before cost reset||Total broken||Total cost||Average efficiency|
|1 use||2 firewalls||0 PWR||0 PWR/firewall|
|2 uses||4 firewalls||2 PWR||0.5 PWR/firewall|
|3 uses||6 firewalls||6 PWR||1 PWR/firewall|
|4 uses||8 firewalls||12 PWR||1.5 PWR/firewall|
|5 uses||10 firewalls||20 PWR||2 PWR/firewall|
|6 uses||12 firewalls||30 PWR||2.5 PWR/firewall|
When playing with Mercenary as a starting program, it will generally be less efficient than this because you often need to hack devices with just 1 firewall, or an odd number of firewalls. Besides average efficiency, consider also the total PWR use — using Mercenary four times per alarm level requires generating 12 PWR every 5 turns, at a rate of 2.2 PWR per turn, which will be difficult to sustain once the PWR from Consoles runs out. Even then, this means using Mercenary less than once per turn, which so you must choose your targets carefully.
Do not fall into the trap of intentionally raising the alarm tracker just to reset Mercenary's cost. The alarm tracker is going to rise if you just wait a turn or two anyway, so Mercenary's cost will reset then, but you can do other things in those turns while you're waiting. It's usually best to wait, even if you only use the extra turns to generate more PWR or let items cool down. That said, intentionally raising the alarm tracker can sometimes be your only option in an emergency, for example when a drone is on overwatch and you need to hack it.
After alarm level 6 there is (generally) no penalty to raising the alarm tracker further, so you can intentionally raise the alarm tracker to reset Mercenary's PWR cost, for example by walking through a Beam Emitter or triggering Blowfish, with no downside.