Based where the attacker places his tapping rig, two types of PowerHammer attacks exists, with two different exfiltration speeds.
The first is "line level power-hammering," and this occurs when the attacker manages to tap the power cable between the air-gapped computer and the electrical socket. The exfiltration speed for a line level hammering is around 1,000 bits/second.
The second is "phase level power-hammering," this version of the attack occurs when the intruder taps the power lines at the phase level, in a building's electrical panel. This version of the PowerHammer attack is more stealthy but can recover data at only 10 bits/second, mainly due to greater amount of "noise" at the power line phase level.