Repair rate is 2*BP*HP/cost, this decreases to 0.5*BP*HP/cost in combat, ie. when the unit getting repaired gets damaged by an enemy unit and for 10s after (BP contributors' combat status does not matter - they still add BP normally when themselves under fire). The total energy cost for 100% repair is half the unit's original cost, so the energy drain per second is equal to BP. Repair does not cost metal. Status effects (slow, EMP and disarm) affect repairers' repair speed, but not the repairee. Repair decloaks the repairers, but not the repairee. Units cannot use BP to repair themselves.
That means given equal BP, repair rate in HP/s among different units is proportional to their HP/cost and repair time is proportional to cost.
This is for repair through buildpower. There is also passive autorepair that happens automatically out of combat, and some units have passive combat self-repair on top of that. The default out of combat autorepair is 5 HP/s after 60 seconds out of combat. Stun through EMP disables this repair (and the out-of-combat timer does not count down while EMPed), but slow and disarm don't. Some units differ there and have it have it kick in faster and more potent:
quote: Banshee - 10 HP/s after 5s Glaive - 20 HP/s after 5s Scythe, most Chicken - 20 HP/s after 10s Kodachi - 10 HP/s after 1.66s (yes, that's almost instantly) Claw - 10 HP/s after 10s Commanders with Autorepair modules - 20 HP/s per Autorepair Module after 10s |
Some units have permanent in-combat passive self-repair. Again, EMP stops it, slow and disarm don't.
quote: Commanders - 5 HP/s Strike Comms: 5 / 5 / 12.5 / 20 / 27.5 / 35 HP/s Ultimatum - 5 HP/s Athena - 20 HP/s Detriment - 30 HP/s Funnelweb - 20 HP/s |
Amphs also have passive self-repair underwater, based on depth. This increases linearly with depth up to a per-unittype limit and is based on the seabed depth and not unit's current depth (ie. floaters benefit from it fully as if they weren't floating). Both EMP and Disarm disable this type of self-repair and Slow decreases it.
quote: Conch: up to 10 HP/s at 40 depth Duck: up to 5 HP/s at 40 depth Archer: up to 40 HP/s at 40 depth Buoy: up to 60 HP/s 30 depth Scallop: up to 10 HP/s at 40 depth Grizzly: up to 40 HP/s at 40 depth Angler: up to 20 HP/s at 40 depth Djinn: up to 30 HP/s at 40 depth |
Finally, Gauss turret has 20 HP/s regeneration as long as it is closed.
All those repair types stack.