Yeah, I will drop powerplants.
Planets (as planets) and cities (so sort of population) will consume energy.
Sources of energy: Gas in converted to energy, also rare resource (Civ 3-5 style) Uranium grants energy.
I wonder about possible energy related technologies (if you have ideas post):
- gas burning enchancer - gas to electricity conversion efficiency +X%
- energy conservation - cities need X% less energy
- fussion reactors - doubled electricity from uranium resource
- maybe some sort of: insulation - cold planets need less energy (but it's confusing if it means cities or the planet)
The mechanic can still be changed/adjusted, so post if you have a good idea.