A while back my corpmates and I were discussing the Ancillary Armor Repairer, a relatively new module added to EVE Online. We couldn't decide if it was better or worse than the T2 armor repairer for long fights. So I did the math using medium armor repairers and graphed it out. I did Medium because I tend to fly Tech 3 cruisers in wormholes.
Since each of the modules uses the same amount of capacitor per cycle (160 GJ) and all have the same cycle time (12s with no skill bonuses), the only way to differentiate them is on their fitting requirements, skill requirements, repair amount, and cost to use.
Fitting: The AAR has the same fitting requirements as a T1 module, eating slightly more CPU than a Meta 4 module. Interestingly enough it's 20 powergrid smaller than the Meta 4. Weird. Anyway, the T2 is much harder to fit.
Skills: All you low-skilled pilots, listen up - the AAR has the same skill requirements as a T1 module. As you'll see below, it's nearly identical to the T2 in repair amount. Why are you still using T1?
Armor Repair: As you can see in the image and Google Doc linked below, with paste, the AAR repairs 4320 HP in 97 seconds. The T2 module only repairs 2560 during that time. However, the T2 module pulls up to 4160 HP at 157 seconds, when the AAR leaves its reload period. This means that the AAR with paste and the T2 module are basically the same in terms of repair amount over time, but the AAR is better for small bursts.
Without paste, you might as well be using a T1 or Meta 4 module. An AAR without paste is awful.
Cost: At the time of writing, nanite repair paste is 26,238.26 isk per unit. One cycle of the Medium AAR uses 4 paste, costing ~105,000 isk. Burning a full set of charges (32 for MAR) will cost you almost a million isk (839,624.32, to be exact). The T1 and T2 armor repairers, on the other hand, cost nothing. Is the AAR worth it? Probably, unless you're going for isk efficiency.
- Never use an AAR unless you have paste.
- If you can't use T2 armor repairers, the AAR with paste is your new best friend. T2 repair with T1 fitting and skill requirements.
- For PvP scenarios, the AAR with paste is better than a T2 repairer because it gives you more HP in less time.
- For PvE scenarios, it's a toss up between isk efficiency and the need to repair burst damage vs damage over time.