>I was also messing around with having the smelters not consume their full amount of power when not actively smelting something. (but held off on that update until I can test it out a bit more).
IMO, this sort of thing will have a big benefit, and will allow you to make the active state an even larger drain.
At the moment, you've only got two choices to help your power situation when you're in immediate trouble; cleaning solar panels, or destroying base modules. Adding the option to idle or shut down things will expand that significantly.
I'd prefer that running the entire system directly off the panels should be impractical, but a bit of management and rationing of your energy supplies and pre-planning your power system would go a long way.The oxygen generators should also go into a low power mode when the base is full of oxygen. 1/10th production and power use perhaps? Some hysteresis should be included to prevent rapid toggles. Or perhaps just a fuzzy logic to smooth things out: 90% oxygen levels = full power mode, 95% = run at half output, 99% = idle.
For the smelter (and also most other things), I'd suggest an off/on toggle. When off, it would consume zero, but cool down and need a minute or so of full power use to become ready to smelt again when you switch it back on. Once warmed up, it would then go into the low power idle state. And when you put stuff in to be smelted, it goes to full power again while operating.
On/off for the airlock would be for the automatic part of it; manual/auto mode essentially.