To throw in yet another opinion that does not help you right now: My friend has a backup server at his place and I have our home lab at my place.

Just a rough calculation: 2 8tb drives for a mirror is 150€ each (during a normal market, and when we bought it), so 300 combined. That is 60€per year if we assume they die quickly after 5years.

With a very light old desktop pc that is power efficient we can reach 25w

That is: 25w/1000 (for kW) * 24h * 365d * 0.35€/kW = 78€ per year of energy.

That is combined 138€/year.

The hetzner storage box is 24€/Month @ 10tb

So that is 288€/year.

So I would argue that its even cheaper to pay a friend to put a small old pc at their place and paying them 40ct /kwh is still cheaper than the clouds? Assuming you can find hdds at a reasonable price. But I could find cheap used offers with a runtime of 3y for 100€.

If you only need 1tb, its not worth it to run your own storage, as the power stays roughly the same:

Hetzner: 3,8€/1tb * 12m = 46.6€ So allone the power of running the backup server is not worth it financially.

For the 5tb plan: 12€*12m=144€ so that is the break even point I assume, as drives don’t scale too mich with price?