It works as advertised all regen gets buffed even when you take energetic[EN] the 0.5 gets a buff.
But as walker you got abilities that drain energy: flood lights, sensor, engine overheat.
- floodlight -1,3e/s without would be -1e/s
sensor -6,5e/s without would be -5e/s
engine overheat -6,5e/s without would be -5e/s
This means that the walker gets a debuff, engine overheat cant hold as long and makes it riskier, less effective and harder to use.
A walker who doesn't has it unlocked yet could hold engine overheat on for 33,33seconds(40[EN]) and someone who has it can only do it for 25s(30[en]), 30% less time. Sure, it times out after 30s but that would still mean that a new walker has some energy left so it can retreat sooner. Or a new walker could still get a full time without needing to have full energy.
It doesn't really make sense that a extra generator would lower the energy output.