To add another data point on energy, in my current
Ride the Lightning Fallen Spire 9/9 game I am now at 44.09.44 up to a maximum cap of 18,290,000 metal storage and tanking most waves on a level 1 spire city. (1093 AIP, 49/120 planets controlled, 11 spire cities, two of which L1)
After the last major attack hitting two different spire cities at the same time (exowave on one, regular waves another) I was running around 107,000 metal/second salvage when the last ship died (and had thus been receiving millions over the duration of the battle), and still managed to run my stores down to a total of around a million and a half metal as I replaced fleet and defense casualties and repaired.
To support my growing fleet and vast distributed defenses, I am currently running 103 energy collectors with a floating balance of 500,000-1,000,000 energy to ensure that I don't get blackouts during small AI incursions wiping out a handful of stations before I contain them. I could possibly get by with one or two score fewer energy collectors, but it would be much more dangerous. Even as is, fully half my planets are completely without any sort of local defenses.
I have unlocked mark three economic stations early in the game (for extra energy primarily, though the metal increase is also good), and harvester upgrades will come soon because the baseline metal income is so very useful to smooth out the resource flow. At this point I could subsist entirely upon salvage without either economic station upgrades or harvesters, but it would significantly have increased risks during the early game.
So where am I going with all this? I don't know how it is ideally
supposed to be balanced right now, and I realize that this approach, taking Keith's challenge and playing AI War with Fallen Spire as a conquest game, is not all that relevant to the balancing of a more normal game of AI war, but I do feel the need to mention that the system seems to be in a fairly good place where salvage/energy balancing is concerned when the game is played that way, both with respects to the sources of metal/energy income and expenditure. (The only thing that is lacking is the ability to build more forts, eating up even more energy, as forts' per-galaxy limits seem oriented towards games with significantly less territory conquered and smaller regular enemy waves.
)
Perhaps spire cities should give less salvage, though it doesn't seem overwhelming to me compared to the metal expenditures. One benefit of doing that would be increasing the value of the strategic choice of not maximizing reactors/shipyards and instead building a few extra habitation centres for their sweet +1000 metal baseline income (~250,000 energy), something that right now is largely counter-indicated. But then again, perhaps it is meant to be that way. I certainly would hate to see spire cities lose their salvage buff entirely, as that would significantly increase the time to recover from attacks thus the amount of time spent and fast-forwarding at high speed while waiting. Perhaps +10% or +15% would be more appropriate?
I will respectfully move, however, that anybody suggesting a galactic cap on converters should have his mouth washed with soap.