If it's only 104% then you could just turn off some other modules Power Distributor and Cargo Hatch should be enough.
Cargo hatch is ok to turn off, but distro its not... quite, its rather one of most critical modules that should be not turned off at any situation
Any bulid that thier COVAS not cryin about "power capacity exceeded" when deploying hardpoints, then its badly optimized bulid.
Set up planetary vechicle hangar to priority 5 or 4, make sure its last "number" on power managment and all critcial moduels should have lower number than this. It will turn off PVH and anything else(if paired to that number) when hardpoint are deployed if total power use is over 100%. If hardpoint are not deployed, and if landed, it will stay turned on these modules. Additonally you can set cargo hatch, FSD interdtictor and fuel scoop (if you got these) also into 4 or 5, as these moduels are not needed when hardpoints are deployed as well.
There is no need to make any changes to powerplant. Most bulids that have litte over 100% power usage, getting over it at + 5% or 6% can be still fully functional if power priority are set up correctly, like 99% of bulids, because random bulids always carring "all" things being mostly "all-rounders", whenver bulid its optimized for specific role or not that does not matter much here.
Correctly power priority are like that; Drives and FSD and power distro should be always at priority 1, and ideally these 3 modules should reach 40% (39%max), then after 40%, things as life support, sensors, and low draw important utilites (heat sink or chaff) can be all at priority 2 up to 50%. Priority 3 are all weapons, shields, SCB, any and all combat modules, then you have lastly priority 4 or 5 of "spare" power, so like already mentioned, things such as FSD interdictor, fuel scoop, FSD booster, any surface type hangars, all "extra" but not neccecary for combat can be setup to be turned off, once hardpoint are deployed. Some of my bulids, are like at 119% power and that extra 20% is being turned off soon as hardpoints are deployed.
40% "priority limit 1" power is when powerplant is being attacked on, and once it reaches 0%, it causes all power output being temporary limited only at 40% capacity, for quite few seconds, and of course any addtional damage done to powerplant (5% chance) can cause ship go boom regadless of hull health left. While npcs rarely are capable to doing that, if being attacked by cmdr, its almost guaranteed for attacker going after plant (or FSD or drives), unless victim ship is paper thin hull and dies in seconds. Regardless, Drives and FSD itself its most vital critcals of them all. You dont wanna lose control or FSD being interupted if plant gets at 0% while unable to allocate pips. I call it hard limit.
Second limit is 50% the "priority limit 2", (from 40% to 50%) because powerplant if under attack but not yet at 0%(from 80% to 1% plant health), can trigger plant malfunction and then its output being limited to 50% for brief moments. Note thats diffrent when plant failure at 0%, this can happen(or not) as there is chance for it, and its quite rare to actually suffer malfunction, as by most cases, plant will be already at 0% before it can trigger malfunction, if thing is being attacked on.
I call it soft limit, becasue sensors and life support, and things alike chaff or sinks, even some low draw weapons, can be put there, as if plant is malfunctionig, these modules if gets temporary off, its still does not hinder any attempt to escape, long as drives and FSD are at 1. Note that if there is no room for distro at "1", using "2" is fine there.
"Limit 3" (from 50% to 99%) all shields, shield boosters, SCB, high draw and any weapons, are should be there. In other words, anything that is needed to combat when hardpoint are deployed. Main reason is when you get plant sniped, you should be not trying fighting back, and shields are already gone, so better use remaing power elsewhere, like for trying high wake.
I like to have cargo hatch at 4 if total power from 1,2,3 are at 97% around but not yet at over 100%, so I can still could scoop materials without need to hide hardpoints, and even if 1,2,3 are 99%, and there is no room for "4" for cargo hatch, it still will turn on, as first, once hardpoints are hidden. Similary for example, FSD Booster can be also having "4" instead of "5", so thing would go online first. Becasue if there is multiple modules that turn on at same time, thier boot times and order wich are turn on, might casue some diffrences.
Anything else, can be at 5 then, so once total is over 100% these will get turned off.
thats in nutshell, how it works. Combat bulids might require diffrent setups, but thats for advanced cmdrs only, and it really depend on bulid itself.
