I've done the calculations just now:

10W constant over 10 years would cost me 275 euro. My hard drives (7 ST2000DL003 and one ST2000DL001) are 10-15 years old now. They're all different batches, none failed yet, so I expect it to last at least 5 more years, possibly a lot more.

The current NAS setup I have (router + DAS + 2 USB) is around 50W. Over 20years it will cost me ~2800 euro in today's prices. So you see, the electricity is a very significant portion of TCO. In fact, it's more than half, because I bought everything second-hand.

Your setup is a tiny niche of a niche. Nobody using a NAS is using tiny 2TB HDDs in 2025 when 20+TB drives are so available.

I feel like you are making your setup more complicated than is even worth and searching for a weird solution when all you need is a RasPi with a big 16+TB USB HDD connected to it.

> 10W constant over 10 years would cost me 275 euro.

€2.30 per month. Which is almost nothing.

> Over 20years it will cost me ~2800 euro in today's prices.

That is €11 a month over 20 years. So the extra 10 watts is still next to nothing even taking into account your exaggerated time frames, which I am dubious as to whether this is real.

I am certainly not going to worry about €11 a month.

You've picked incredibly long time ranges and you still have small numbers.

3k over 20 years is literally nothing.

It's lost change in the couch compared to almost any other financial decision you could make.