[pedantsamaritan]

There are a lot of light bulbs, though. The LED switch has had meaningful impact on US residential energy usage [0]. IEA reports 38B in LED sales in 2015-2020 [1]. Averaging $10 (high) per bulb, that's 3.8 billion bulbs (including non-residential).

Leaving a light on doesn't matter much. Leaving billions on can clearly have an impact.

[0]: https://archive.is/RldJl

[1]: https://www.iea.org/reports/lighting

[kwhitefoot]

The billions of bulbs have the same proportional impact on the national energy budget as the few in your home have on yours, that is practically nothing.

See David MacKay's Sustainable Energy Without The Hot Air, chapter 19. https://www.withouthotair.com/c19/page_114.shtml