The S21+ Hyd is the best-returning machine on our floor

47% in year one, 395 TH/s from one box at a settled entry price. Seventeen months in, here is what it has banked and what is left in it.

Bitmain Antminer S21+ Hyd (395 TH/s)

Seventeen months in

A 395 TH/s S21+ Hyd at 15 J/TH, bought at $5,709 and landed at $9,007, running at 6¢ since April 2025. It has mined and kept 0.0834 BTC in 525 days — worth about $6,779 today — for $3,452 of electricity, about $41,400 a coin.

$3,327 of cashflow, about 37% of its landed cost, on a machine well under half way through its expected life. It ran 239 days in Argentina and moved to Nigeria on 9 December 2025, the month Nigeria started paying better for it.

Chart: Banked so far, and where the forward figures put it by the 2028 halving.

Why the hydro version returns more

This machine returns about 47% in its first year at our Argentina site — the highest figure of anything we currently host, ahead of both air-cooled S21 variants despite the S21 Pro making a slightly cheaper coin.

The reason is density. Freight, import duty, customs, rack space and setup cost roughly the same for a 225 TH/s box as for a 395 TH/s one, so a hydro machine spreads them across nearly twice the output. At 15 J/TH the efficiency is already good; the per-terahash overhead is what turns good into best.

That only works if your site can take hydro. Ours can — Argentina and the UAE both run water loops — which is why we stock these rather than treating them as a specialist item.

395 TH/s in one box spreads every fixed cost over nearly twice the hashrate of an air-cooled machine.

What is left in it

At today’s difficulty and with bitcoin back at its previous high, it has another 0.098 BTC and roughly $7,519 between now and April 2028 — the largest forward figure of anything in this generation we host. That lands it around 1.2× its full landed cost by the halving, with a long life after it.

At 15 J/TH it will still be clearing at 6¢ after the next halving and has years beyond that at Nigeria’s 3.9¢. Seventeen months in, the machine is barely a third of the way through what it is going to do.

Bitmain Antminer S23 Hyd (563 TH/s) — 9.5 J/TH, In stock, $31,017 of electricity per bitcoin, 28% year one
Bitmain Antminer S21j XP Hyd (495 TH/s) — 12 J/TH, In stock, $39,035 of electricity per bitcoin, 42% year one
Bitdeer SealMiner A3 Pro Hyd (666 TH/s) — 12.5 J/TH, In stock, $40,282 of electricity per bitcoin, 34% year one

The machines that make cheaper bitcoin than this does.

Which machines this covers

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.