Active Modules....What Do They Actually 'Act' On?

Let’s say you have a ship with shield extenders and showing 40K EHP with those. You add a Multispectrum Shield Hardener, and that raises the EHP to 50K.

OK, so if you apply that active extender before combat then theoretically you get the full 50K EHP from the start. But, here’s the question and the bit where I am confused…

What if my shield is half destroyed and I then apply the shield extender ? Do I get the full 10K of shield extension I would have got had I applied the shield extenders from the start, or do I only get an extra 5K as the shields themselves are half destroyed ? I would think it would be the latter…but I cannot find any documentation that specifically says so.

The main reason I ask this relates to Assault Damage Control. If the latter answer is correct above, then that would mean one needs to apply Assault Damage Control as soon as possible on being attacked…as to leave it would actually result in less benefit. That surely has to be correct…as it doesn’t make sense to me that my ship could be down to all shields gone and 1% armor left and then hitting Assault Damage Control could magically give the full 180K EHP I’d have got with full shields and armor. But is that correct ?

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The Assault Damage Control increases resistances, not HP. Resistances affect incoming damage equally regardless of the actual amount of HP remaining.

EHP (Effective HP) is only a calculation of the HP equivalent you would have based on your current resistances, if your resistances were all 0%.

Specifically for shields there’s a timing factor involved; passive shield regeneration is highest at 25% capacity. Activating the Assault Damage Control around that point would provide the highest amount of passive shield regeneration. But you’d likely have active shield regeneration, so this effect would be rather minor.


Hello Zemara,

thank you for your question.

To answer your question, we have to answer a different question first: how is EHP calculated?

EHP is short for effective hit points. It is a cumulation of all your HP values combined with all your resistance values. It is not a stat that is used for any kind of calculation. Rather, it is an approximate idea of how many hitpoints your shield / armor / hull has if accounted for all resistances.

EHP on your fitting screen is calculated with all your hitpoints at full value. If you were to take damage during combat and activate a resistance module, it is only logical that your EHP value would be diminished: Your effective EHP derives from the HP that you actually have left.

You have remarked the lack of documentation surrounding this issue. You have my permission to print and share freely this indepth analysis as many times as you wish.

With helpful regards
-James Fuchs

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  1. the hardener’s effect is calculated making use of the base resist values

  2. shield extenders don’t have stacking penalty

  3. Let’s forget for a moment that “EHP” is a highly theoretical value that is normally only calculated on hull/armor/shield HP’s at max and with the available resists in the fit, and pretend we can calculate it at any moment in time for the condition the ship is in at that moment.

in that sense your newly onlined shield extender should give it’s full individual HP (which is not EHP)


you will not get 10k EHP boost all of a sudden by onlining the extra extender, because that 10k EHP was originally calculated on full shields HP and the relevant resists. Now it will be calculated on less than maximum (your half destroyed shield).

P.S. you could mimick this in a fitting tool (pyfa, or the ingame one) by swapping one of your extenders to a smaller one (as if the larger one were half broken)

In case this was a typo, and you meant “shield hardener”, it still wouldn’t be 10k EHP extra all of a sudden. The hardener has no effect on the HP at that moment, only on the "effective"hp calculation. IF your shields were at max HP then obviously you get the 10k, but with your shields at 50% so will your shield EHP be at 50%.

The formula for EHP is simply HP/(1 - average resists) - for omni. And that includes hull, armor and shield, so it’s not very accurate, since apps will take the average resists across these layers, downplaying the layer that is the most significantly “beefed up”
For the sake of simplicity, let’s assume a ship with 1000 hull hp, 2000 armor hp and 4000 shield hp. Your average resists are .6 with the hardener ON (60 %, in H/A/S). Your total HP is 7000, your EHP is 7000 / 0.4 = 17500. With the hardener OFF you have e.g. an average of 40%. Your EHP is then 7000 / 0.6 = 11667. In this case, by switching the hardener ON, with FULL shields, you get an extra 5833 EHP.

Repeating this for a half broken shield (2000 iso 4000), your total HP is 5000. With hardener ON have 5000 / 0.4 = 12500 EHP, without the hardener it’s only 5000 / 0.6 = 8333, you only get a push of 4167 EHP (compared with a push of 5833 EHP with full shields)

Edited after fruitful discussion with @Uriel_the_Flame

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Edit: After @Wadiest_Yong tested it it was proven the below is incorrect and it works as he initially suggested.

Even if we were to talk about SHP (shield hitpoints) instead of EHP, onlining the shield EXtender (not hardener) mid-fight would only increase the maximum (possible) shield HP but the current amount of shield HP would remain at its current value (and decreased by incoming damage).

So onlining the extender would not add extra shield HP it would just grant a greater upper limit (and by doing so would also increase passive shield regeneration as an additional effect).

How so ? It’s meant to increase SHP as such. Onlining it should result in an increase in HP (and EHP), like onlining an armor plate does.

Edit: After @Wadiest_Yong tested it it was proven the below is incorrect and it works as he initially suggested.

EHP is the theoretical total not the current actual. The module increases the total not the current amount, that is done by shield boosters which add to your current amount of shield HP (just like passive regen) and can reach the current maximum that way (and if your extenders burn out due to effects of overheating modules or you offline them then your possible maximum decreases accordingly).

Boosters are repping modules. They will of course have an effect on HP/EHP during combat. Extenders add base HP (hence EHP) and will also influence passive shield regeneration. That is correct.

But what @Altara_Zemara was asking, does onlining an extender resp. activating a hardener give me the full 10k extra when my shields are halfway down, the answer is: your EHP will increase when you online your extender (you get your extender’s HP bonus / (1 - average resists)), or start using your hardener (in which case average resists go up) but not to the full amount as if you were at full shields. So that’s a situation at a specific point in time. One can of course calculate EHP at any point in time, just like one can break it down for hull, armor and shield respectively. Not sure if any app does that.

If Altara’s question is “will my theoretical EHP i.e. max EHP value get the 10k” then the answer is sure, but it doesn’t have any meaning.

Edit: After @Wadiest_Yong tested it it was proven the below is incorrect and it works as he initially suggested.

I think this example illustrates well what I was talking about:

You have a ship with 4x shield extenders but only have 3 of the 4 online. You undock. Your ship has 100% SHP right now.

Now while in space you online the fourth shield extender (4/4). Now your ship has less than a fully charged shield and slowly will start accumulating SHP according to passive regen (and if activate those shield boosters).

Thus activating additional shield extenders mid-combat will not grant you extra current SHP just potential max. SHP.

I’ve honestly never done that in 13 years :smiley: I’m going to try this !! I assumed you received the hp from the 4th extender immediately. If not, then @Altara_Zemara is in bigger trouble, lol. Thx for the heads up. I’ll stick to armor plates :stuck_out_tongue:

It was many years ago I’ve played around with these but that is how I recall it went. But make sure to let us know if your experience differs.

It sure does differ. Here’s a (passive) drake with one offlined extender
onlining the extender again (with the usual cap drop):

the effect of the onlined extender is immediate, it doesn’t have to “regen”, you get it as “full shield”.

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Hmm could you try if the shield is not at 100%?

Let me see if i can find some friendly npc’s to damage my shields with the passive tank off (i’m in hisec)

Yep, onlining the extender acts immediately, both on max HP and on current HP. So it comes on fully “loaded”.

Your OP mixes up several terms, which lead to some replies that probably aren’t specific to your question.

A Multispectrum Shield Hardener is a resist module. It makes your shields more resistant to damage, ie., they take less damage from a hit of any type that they resist. So for a Hardener, you want it on as early as possible. Every hit that you allow in without turning it on does more damage than it otherwise might.

That’s why you get “effective” HP, not real HP: if you have 1,000 shield HP and incoming shots do 100 HP damage each, your shield can take 10 hits or 1,000 HP of damage. If your shields offer 20% resistance to the incoming damage, then each incoming 100 HP of damage only removes 80 HP from your shield. Your shield now lasts for 12.5 incoming hits or 1,250 “effective HP”, even though it still only has 1,000 shield hit points.

A shield extender actually adds base HP to your shield. So an 800 HP Medium Shield Extender would increase your shield from 1,000 to 1,800 base HP, but it would still take full damage from each incoming hit unless you add resistance modules. It is a passive module so would not be activated or on-lined in mid-battle (in general).

You can think of any “resistance increasing” module as a “Current Hitpoint Multiplier”. It increases the ‘effective’ amount of any HP you currently have by reducing the incoming damage. So it has greater effect the more HP you already have.

An Assault Damage Control gives passive resistance that’s a little lower than a regular DC. However it can be activated to give much stronger resistance for a short time, 10 seconds IIRC. So you would generally activate when you need 10 seconds of greater protection, not based on your “current” HP. Eg., when you need 10 seconds to escape, or to resist 10 seconds worth of very high incoming damage while you whittle down the opposition. Or to give your active repair 10 more seconds to build up more HP, etc.

So hitting activate on your ADC right at the start might not be wise (your active repair might be enough to negate incoming damage at that point, or the incoming damage might no be high enough to need it). But activating it at 1% armor left also won’t be wise - as you say it won’t magically add to your current HP.

It’s complicated to picture it all at once, but understanding the full interplay of your base HP (shield/armor/hull), their native resistances, active repair sources, passive regeneration (for shields), resistance modules; and balancing those against incoming damage while you work to remove the sources of incoming damage, is the end goal. It helps if you can envision 3 graphs and a threat-priority point-plotter in your head simultaneously.

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No rush and thanks for testing it for us.

To add more complexity to the situation: Also below 25% shield (if I recall correctly) damage can bleed through the shield which is affected by a related skill as well how much of that your pilot can prevent. Thus letting your shield go way down is not a good idea, also because if it reaches to zero or close to it the passive regeneration rate goes to a minimum so it will take ages to get back up again despite at around 25% or such you have peak passive regen rate.

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Resistances reduce the damage you take.

To make optimal use of an ADC, activate it when you expect a lot of incoming damage during the duration of the module.


Edited my previous post with the answer: onlining an extender has immediate effect on current and total hp, so it onlines fully “loaded” with available hp. It’s a nice boost, but you lose the cap, so it’s a pretty bad way in most cases.

EHP is, as you indicate a very rough estimate. There’s other aspects, like the passive regen, the bleeding into armor etc that make it even less reliable.


Thanks for confirming, this means I’ve remembered incorrectly. Good to know for sure and avoid the mistake in the future.

Or when you need a bit of pause to reload stuff including cap boosters, want to repair stuff with nanite or get low on cap and such where you need to do something to survive a critical aspect of the fight.