Scaling Type:
No real scaling but radius do increase depending on size multiplier on pickup
Detailed Explanation
Electric Plug triggers whenever you take damage, releasing an electric shock that can hit up to 11 enemies in range. It deals damage based on your level and damage multiplier:
It also applies a small knockback equal to 1.5 × your knockback stat.
The shock radius is:
However, the radius is only recalculated when you pick up a new Electric Plug. If your size increases after obtaining one, the radius does not update until you collect another copy. This can cause extra plugs to either provide no benefit or noticeably increase the radius depending on your size at pickup. This behavior may be unintended.
$$(8 + \text{PlayerLevel} \times 0.8) \times \imagetooltip{Damage Multiplier}{https://res.cloudinary.com/dft1n3spr/image/upload/v1764501733/megabonk-guide/msyfbhopicnivvxuy6tk.png}$$
It also applies a small knockback equal to 1.5 × your knockback stat.
The shock radius is:
$$\text{Radius} = 12 + (4 \times \text{SizeMultiplier})$$
However, the radius is only recalculated when you pick up a new Electric Plug. If your size increases after obtaining one, the radius does not update until you collect another copy. This can cause extra plugs to either provide no benefit or noticeably increase the radius depending on your size at pickup. This behavior may be unintended.
How it Stacks
Additional copies do not increase damage. Their only potential benefit is recalculating the radius based on your current size multiplier.
Picking up a copy at the same size = no change
Picking up a copy after increasing size = larger radius
If you pick up an Electric plug when your size is 1.0x and later increase your size to 2.0x or more, the radius isn't updated at all before picking up a second copy.
So multiple copies does not do anything on their own, but just relies on the size multiplier at the time of pickup. This is most likely a bug as it looks like it should be able to hit more enemies than 11 when you get multiple copies, but currently, this is not the case.
Picking up a copy at the same size = no change
Picking up a copy after increasing size = larger radius
If you pick up an Electric plug when your size is 1.0x and later increase your size to 2.0x or more, the radius isn't updated at all before picking up a second copy.
So multiple copies does not do anything on their own, but just relies on the size multiplier at the time of pickup. This is most likely a bug as it looks like it should be able to hit more enemies than 11 when you get multiple copies, but currently, this is not the case.