True! Every watt you can save without reducing your hashrate, is directly correlated to more money in your pockets. That's also the reason GPU miners draw less power from their cards than gamers. They aim treading a very fine line between as low current settings as possible, while keeping the chip stable and running at reasonable frequency / hashrate.

Also, never forget that for reducing greenhouse gases, we need to (1) transition machines to run on electricity and then (2) generate that electricity cleanly. In Bitcoin mining (opposed to gold mining) this first step is already given, which is great.

This reminds me of a video a while back: https://www.youtube.com/watch?v=IZEaYjo4ZJU
They acknowledge that solar energy has a storage problem and that batteries are needed. However, it's a known fact that the Lithium supply is not endless and getting it out of the earth is not great, either.
That's why overbuilding renewables (e.g. to have enough sun even in winter) and using the excess for Bitcoin mining is a better / alternative solution.

To be honest, I think NotATether is right. As far as I know, there are no 'reserves' of ASICs ready to turn on as soon as the Bitcoin price skyrockets. They may relocate if it gets too expensive to mine somewhere (either by moving own operations or selling the devices and closing a facility), but they essentially keep running at all times.