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Progress report · Oct 28, 2026 · 4 min read
631 days in Argentina: the Antminer S21 XP was never off, and never within $8 of its power line
Bought in February 2025, the S21 XP has hashed every day since in Argentina, and network hashprice has not once come within $8.30 of what its power costs. It has covered about a third of its box so far. The halving is the test, and it points to Nigeria.
Bitmain Antminer S21 XP (270 TH/s)
Bought at a $57.60 hashprice, and it has hashed every day since
The first price we hold for the S21 XP that had settled, on 5 February 2025, was $24.68 a terahash: $6,691 for the 270 TH/s unit, $8,914 landed in Argentina with freight, duty and setup. Network hashprice that day was $57.60 a petahash a day on our hashprice chart. The machine went to its home site, which is where air-cooled machines start, at 6¢.
In 644 days it has been off for 0 of them. It has not crossed to Nigeria: the one move a machine makes is made when a year of figures says cheap power pays decisively better, and for the S21 XP that year has not said so yet. Our review of the machine has the spec, which is 270 TH/s from 3,645 W at 13.5 J/TH, and what it costs to run today.
What 631 days banked
Over those 644 days the S21 XP has mined and kept 0.0830 BTC for $3,503 of power. At today's price that is $3,139 of cashflow against a $8,914 landed cost, 35% of the box so far. That is a third of the box in about 21 months of a four-year life.
Electricity has averaged about $42,200 a coin over the run. Today's coin costs more: about $45,400 in Argentina, because hashprice has fallen since the start. The lifetime average is the history, and the figure to plan on is today's.
Never switched off in 631 days, and every coin it mined is still in the wallet.
The line it has never touched
A machine's line is the hashprice at which it stops covering its own power. At 13.5 J/TH a petahash uses 324 kWh a day: $19.44 at Argentina's 6¢, and $12.64 at Nigeria's 3.9¢. Since the day it was bought, hashprice peaked at $63.80 on 11 July 2025 and bottomed at $27.74 on 6 June 2026. That low was $8.30 above the 6¢ line, 1.43 times it.
On 357 of the 630 days from purchase to 27 October, hashprice was at least twice the line. It was $35.95 on 27 October, 1.85 times the line at 6¢. Our count for a 19 J/TH machine shows that a dearer line has not been crossed either.
The halving test, and where it puts the machine
The April 2028 halving halves the coins a petahash earns. At today's price and difficulty that puts hashprice near $17.97, which is $1.47 under the 6¢ line and $5.33 over Nigeria's. That is today's conditions held flat, not a forecast; it is why every projection we publish assumes the old high returns.
So the S21 XP is an Argentina machine for the run to April 2028 and a Nigeria machine after it. The one move it makes is made once, and the guide to crossing explains why. Between now and the halving the engine has another 0.065 BTC in it, worth about $8,050 with bitcoin back at its previous high of $124,493: roughly 1.3× its hardware by then. The guide to efficiency and halvings shows where each J/TH puts the line.
The same machine costs less to get into today
The 270 TH/s unit is $3,119 today, $11.55 a terahash, the lowest we have held for it, against $24.68 when we bought. The hashrate is the same and the efficiency is the same. It is the best entry price the machine has had. Bought today and racked in Argentina it returns about 33% in year one at today's price and difficulty, and 35% in Nigeria.
Against the newer air machines it sits where its efficiency puts it. The M74S+ at 12 J/TH makes a coin in Argentina for about $40,400, against this machine's $45,400, and asks $14.86 a terahash against its $11.55. The S21 Pro is $50,500 a coin at $8.61 a terahash.
What a fault costs, and what the record says
We looked for operator threads on the S21 XP and found none we could cite, so we do not give a failure rate. What exists is a repair shop's reference. D-Central's S21 XP repair page says each board carries 91 BM1370P chips in 13 domains of 7, so a failed chip can take its domain offline, and that the most common fault is incomplete chip detection. It says its patterns come from public sources, not internal failure rates, and we treat it the same way.
What a fault costs is the part that matters. In Argentina we repair on site and bill the cost of the parts only, and an air machine is serviced where it hangs: a failed hashboard is a line item, not a catastrophe. This machine has run 631 days without a day off.
What we would tell ourselves
Buy the efficiency and the power rate, and let the box be the cheap part. The S21 XP cost $24.68 a terahash to get into and costs $11.55 now, and what it earned in between did not depend on either number: 0.0830 bitcoin, kept.
For a miner the lesson is where the line sits. At 6¢ this machine has had the room it needed for 631 days, and the halving will want Nigeria's rate. A machine on 3.9¢ has $5.33 to spare at half of today's hashprice, which is a very different position from $1.47 short.
Sources and further reading
- Antminer S21 XP repair — D-Central, 2026
Which machines this covers
The other side of this machine
Bitmain Antminer S21 XP review — The most efficient air-cooled machine we stock, and the one we put S19-era buyers into. At 13.5 J/TH it makes a bitcoin for roughly 40% less electricity than the machine it usually replaces.
Disclosure
Firsthand Bitcoin sells and hosts mining hardware, including this machine. No manufacturer, distributor or affiliate programme paid for or reviewed this page and we take no commission on the links above. Historical figures are computed from daily bitcoin price and network hashprice, each day valued at its own prices. Nothing here is investment advice.