I'm posting this as more of a "fun thought" than anything else.
It's generally considered a fact that Linux, along with many other open-source software projects, are more efficient than their propriety closed-source counterparts, specifically in terms of the code that they execute.
There are numerous reasons for this, but a large contributing factor is that open-source, generally speaking, incentivises developers to write better code.
Currently, in many instances, it can be argued that Linux is often less power-efficient than its closed-source counterparts, such as Windows and OSX. However, the reason for this lies not in the operating system itself, but rather the lack of certain built-in hardware support for Linux. Yes, it's possible to make Linux more power-efficient through configuring things differently, or optimizing certain features of your operating system, but it's not entirely uncommon to see posts from newer Linux laptop users reporting decreased battery life for these reasons.
Taking a step back from this, though, and looking at a hypothetical world where Linux, or possibly other open-source operating systems and software holds the majority market share globally, I find it to be an interesting thought: How much more power efficient would the world be as a whole?
Of course, computing does not account for the majority of electricity and energy consumption, and I'm not claiming that we'd see radical power usage changes across the world, I'm talking specifically in relation to computing. If hardware was built for Linux, and computers came pre-installed with optimizations and fixes targetted at their specific hardware, how much energy would we be saving on each year?
Nanny Cath watching her YouTube videos, or Jonny scrolling through his Instagram feed, would be doing so in a much more energy-efficient manner.
I suppose I'm not really arguing much, just posting as an interesting thought.
Yes, I probably should have rephrased that as "are often more efficient" rather than implying that this is always the case. I do think, and I mentioned this somewhere else, though, that it's quite a hard comparison to make. I'd probably make the argument that if the driver itself was the issue, making the driver open-source would likely (and that's a "likely" going off an assumption which I can't back up) be more efficient.
Generally speaking, my point does still apply for fully open-source software which has been developed specifically for Linux. Unfortunately, we won't be seeing much mainstream Linux-bespoke software for a while, at least not until the year of the Linux desktop finally arrives.
I completely agree with what you're saying, though.