"Refurbished" sounds like factory condition, and in consumer electronics it gets fairly close. Bitcoin miners start from a different place. These machines come out of continuous operation in data centres and mining farms, often after months or years under full load, heat and dust.
This article explains what you can actually expect, and which marks are explicitly not defects.
Refurbished is not a protected term
There is no standard, no certification and no legal definition behind the word. Every seller decides for themselves what it covers.
In practice that ranges from "dusted off and resold" all the way to "fully stripped, components replaced, retested". With ASIC miners, most of the market sits somewhere in the middle, and that gap is exactly where misunderstandings come from.
We take the opposite approach. Instead of leaning on a term that promises a lot, we would rather describe precisely what we do.
What refurbished means at 21energy
Every used miner goes through the same process before it leaves our warehouse.
Tested
The miner is powered up and checked for full function. Among other things, we verify:
- hashrate and stability under load
- all hashboards and their chips
- fans and thermal behaviour
- power supply and control board
Units that fail any of this do not go on sale.
Cleaned
Cleaning is done by hand, in several steps:
- Compressed air to blow dust out of heat sinks, housing and gaps
- Damp cloths for the case and the grilles
After that the miner is clean and free of dust in every area that matters. What it does not become is factory fresh, and that was never the goal.
Said upfront
Every used miner is labelled as refurbished in the shop, and this article is the detailed version of what that label means.
What we do not do is grade or individually photograph every single unit. Condition varies from machine to machine, and a per unit promise is one we could not reliably keep.
What we do commit to is the standard: tested, cleaned, and open about the marks that a life in a data centre leaves behind. The next section lists exactly what those are.
Signs of use that are normal, not defects
A miner out of a data centre carries its history with it. The marks below show up regularly, have no effect on function, hashrate or lifespan, and therefore do not count as defects.
- Dust residue in hard to reach gaps. Between the fan blades, under the protective grille and in narrow spots inside the housing, compressed air and a cloth simply cannot reach everywhere. Some residue stays behind.
- Occasional rust spots on the grilles. Data centres are warm and sometimes humid. That leaves small rust points on grilles and sheet metal edges, and they cannot always be removed completely.
- Remnants of permanent marker. Farms label their machines with marker pens for rack positions or maintenance notes. Those markings are waterproof and do not always come off entirely.
- Slightly bent spots on the housing or grille. Miners get racked, unracked and shipped in a data centre. Small dents or marginally bent edges are the result.
What is not normal, and what we do not ship: dead hashboards, failed fans, unreachable control boards, or a hashrate well below spec. If a unit arrives with a problem like that, contact our support and we will sort it out.
Why we do not polish them to look new
We could respray housings, swap out grilles and cosmetically restore every unit. That would have three consequences:
- The price would go up without adding a single TH/s.
- The effort would deliver no technical benefit.
- A polished case would imply the machine is new.
Used miners appeal to people who want as much hashrate per euro as possible. So that is where we put the effort: into testing and function, not into looks.
When a new miner is the better choice
Used is not always the right call. A new unit makes more sense if:
- the miner sits visibly in your living space and appearance matters
- you want a manufacturer warranty on a sealed, boxed unit
If your priority is hashrate per euro invested or an affordable way to get started, then a refurbished unit is usually the more economical decision.
