Considering the low energy cost for the stuff I've built so far, I don't think it is going to be a big issue. I've yet to build Planetary Defense and Mind control which may be BIG consumers. But then they would have to be, otherwise it looks like I can support everything in my old build with a single power plant, assuming it is running at full capacity.
Long Range Sensor 1+Long Range Sensor 2+Mind Control+Matter Synth 1+Matter Synth 2+Military Base+Slingshot+Planetary Defense+Any of the power plants=100.5% of your planets income in upkeep. So there are definitely choices you have to make or your planets will never build a single ship.
