[Vegenoid]

"Used" doesn't magically wave away the carbon/resource cost of producing the hardware. Buying used hardware still stimulates demand for the production of new hardware, although to a lesser extent than buying new.

Buying used also only works when not that many people are doing it. On an individual level, it is a good thing to do, but it isn't a solution. It does help foster an environment of maintaining and supporting hardware for longer, which is a better solution.

I could envision a scenario where solar self-hosters replace hardware at a rate so much lower than than hosting companies that it outweighs the additional hardware it requires, but I don't think it is the current reality.

[nine_k]

It reliability waves away the costs of producing hardware for this particular project.

The second-hand computer and second-hand panels have already been produced for someone else, their cost is sunk. But their value can continue with this project, or end with the hardware and panels going to a dumping ground.

[Vegenoid]

Again, no it does not. When someone buys a new RPi, it was already made. The cost of making it was already sunk. Buying it gives the company that made it more money, and encourages them to make more.

If you buy a used RPi, it gives money to someone who buys new computers, and encourages them to buy more. It stimulates demand for the production of hardware, just like buying new stimulates the production of new hardware, even though the hardware you bought had already been built.

Yes, it is to a much lesser extent than buying new, but it certainly isn’t zero. And again, it only works on a small individual level.

It is a good thing to do, but it does not zero out the cost of producing (or running) the hardware.