Currently, the walls only drain energy while they are reconstructing. Adding a constant power drain to walls when they aren't being attacked might be better for balance when considering it based on total walls.
Without such a drain, the energy consumption of your walls will depend on how much they are damaged or destroyed - so a base with low pollution, high DPS defenses and a biter free zone around the walls will currently have much lower Stormwall energy demand than a deathworld on burners.
I also usually play with a "walls block spitter projectiles" mod, which increases the damage walls take per attack.
The difficulty of balancing this is that the default should be sane on both relatively easy playthroughs (slow evolution settings, solar energy (=low pollution), large contiguous base (low surface per base area), no difficulty mods) and challenging ones (deathworld, Rampant, mods that add a long burner phase, very fragmented base (individual outposts) with large surface (=many walls for smaller usable area)).
Another question is whether to incentivize "box bases" with a high base energy drain - I'd rather keep the main energy consumption in regeneration (ie. scaling with attacks, and requiring an investment in storage/capacity overhead on top of that for laser turrets) and allow high numbers of "inactive" walls (normal walls don't cost you anything after they are built either).
What kind of modpack and scenario did you get these values from?
