How much power can an update even use?
Good question. And I've been thinking about this. So I guess it depends. Especially on my assumptions.
So assume I'm environmentally friendly. I know that leaving things on stand-by means it's still using power. So I hit DBRB when I'm done. So Win11 already allows 'off-peak' updates, ie you can schedule between say, 3-4am. PC can wake from sleep, do it's thang, and sleep again. Except when it doesn't, but MS is as MS does*.
So how then would the PC know 97% green electrons are available NOW! and it should wake up, update, and shut down again. So I guess if electro-sensitives want to take advantage of this new, green feature, they'll end up using more energy to keep their PC's in sleep mode. And much more if the update doesn't return their PC to sleep, or shut down.
So I think the answer would be some small fraction of a penny or cent. A more interesting question is the value to MS. So it would know the timing. It would know your energy supplier. It could combine data to give you a nice notification that the last update cost you 0.003p, but if you switched to Bulb Energy, it would only have cost you 0.0027p!**
I'd be all for implementing it, but with things where that really matters like charging electric cars.
That's coming. Kind of. So new UK home charging installations are supposed to be run via a seperate 'Smart' meter. The 'smart' being the ability to go 'nope!', or charge a higher tariff. Fuel duty has to be replaced with something. And if 'smart' consumers decide to just plug into their normal supply, telemetry & black boxes mandated to all new cars would report the duty evasion.
Now for those who have solar panels and don't have net metering, using renewable power when you have it can save you money.
That's really the use case for solar, ie use the energy you're getting for 'free' while it's available. But it's probably also a use case where the feature won't work in Win11, Even though your solar panels are generating 100% 'renewable' energy, there'd be no way to signal that to the PC. Ok, with some creative engineering that may or may not be to code, you can. So run solar to a UPS, run PC off that, and have a changeover so you're not using grid power whilst solar is available. So then if the PC's set up on a 'solar only' power segment, if it's got power, it's on renewable.
(why you'd want to go to those lengths is a seperate question. It won't be compatible with Win11 though.)
*I think PCs afflicted by the MS virus develop insomnia. You put them to sleep, but sometimes they'll wake again and wait patiently for their user input.
**Terms and conditions apply. Price indicated is for our special introductory tariff. After your initial 30min trial, you will be re-enrolled in a 720 month, variable tariff contract. Lubrication not included. So when 'renewable' subsidies are ended, your 100% renewable contract may result in frequent power cuts and far, far higher prices.