Talking to new players, I encounter many misconceptions and confusion surrounding the concept of Eve’s stacking penalty system. Some don’t understand what the stacking penalty does; many others do, but don’t see why it’s in the game. I’ll try to get everyone up to speed, but the second point will take up the bulk of this article.
The basic idea is that stacking penalties reduce the effectiveness of multiple ship modules affecting the same ship attribute. Eve University has a basic explanation, eve-wiki has a better one, but they still only provide a brief overview.
What stacks without penalty?
- Implants (except for Snake implants)
- Combat boosters
- Damage Control
- Skills (including piloting skills that give ship bonuses)
- Engineering boosts (CPU, capacitor size and regen, powergrid, shield regen)
- Anything that adds raw numbers (i.e. armor plates, shield extenders) rather than a percentage
- Shield and capacitor recharge
- Cargo hold size
What definitely is stacking penalised?
- Weapon damage and rate of fire percentage bonuses from modules or rigs
- Weapon range bonuses
- Sensor range and scan resolution
- Shield percentage changes and repair bonuses (rigs, shield boost amplifiers)
- Armour percentage changes and repair bonuses (rigs, regenerative plating)
- Electronic Warfare (both boosts, and the effects)
Note that penalties are stacking nerfed as well as bonuses. This makes multiple capacitor power relays a viable option for shield-tanked ships, and means that target painters and shield rigs stack against each other (don’t worry, your signature radius will still be huge; just slightly less huge)
Everything else is a maybe.
Why are modules stacking penalised?
The quick answer is, “because players are min-maxing bastards.”
A longer answer is that players like to optimise their ships for their intended role. If their ship is designed to kill things quickly, they will want to fit modules that maximise its damage capability. Similarly, if the ship is a bait ship, tank is maximised at the expense of everything else.
However, the problem lies with percentage bonuses.
With a non-percentage bonus, each additional module provides the same increase in a linear fashion. Add two 1600mm plates, and the enemy will take twice as long to chew through them compared to only fitting one. In the graph above, it’s the grey line.
With a percentage bonus, each module you add becomes more powerful, based on the number of existing modules. This rapidly gets out of hand. The red line in the example is how much damage a ship would do with tech 2 damage modules without a stacking penalty. Note that the graph only goes to six modules, but in some cases, a full eight could be fit (and in the case of an Iteron V and its rigs, often are fit). Increasing a gank ship’s damage to more than triple would just wreck game balance; as would buffing resistance bonuses for tanky ships. It would be (and by all accounts was) an un-fun game full of extreme fits with less interesting gameplay.
To solve this, CCP added module stacking in the Red Moon Rising expansion in 2005. As can be seen, adding a single module remains unchanged; adding a second keeps the slight boost due to percentage compounding, but the third module is back down to the linear level, and it gets downhill past that. This has the effect of nerfing those modules down to a near-linear progression, meaning that the defensive modules such as plates and shield extenders can catch up, but if you don’t fit them, you aren’t destroyed instantly.
In summary: you may hate the fact that module stacking makes your fit not as awesome as you’d like, but you wouldn’t like the alternative.