I feel like changing the time requirement and just boosting the energy requirement to a set value doesn't necessarily make sense. That would infer that researching nuclear power is just as intensive as researching how to fill in a water hole, but takes more time.
My thought is instead of having a set power level and varying the time required based on what packs would have been used, keep the time the same as default for the different researches, but boost the power requirements based on what packs would have gone into the research. No idea if this is possible or not, but I feel like it makes more sense.
