Antminer S21 Efficiency: 17.5 J/TH in Practice

The Antminer S21 is specified at 200 TH/s, 17.5 J/TH and 3500 W. Hashrate tells you gross output, efficiency tells you what that output costs to produce, and wattage tells you what circuit you need. Only the second number survives a difficulty increase intact as a comparison tool.

Tolerance matters too. Manufacturers publish plus or minus five percent on hashrate and power, so two identical machines can differ measurably. We publish the measured figure for the specific unit you are buying rather than the datasheet band. measured wall draw versus datasheet efficiency.

Rated efficiency assumes a controlled intake temperature. Every few degrees of additional intake heat costs a little hashrate and a little efficiency as the machine protects itself. Sites that manage intake air well routinely outperform sites with identical hardware and poor airflow.

That is why hot and cold aisle separation, filtration and positive pressure are not optional refinements. They are the difference between running at spec and running at ninety percent of spec for the life of the fleet.

Plan for 3500 W of continuous draw plus headroom for inrush and cooling. In practice that means a dedicated 200-240 V circuit sized correctly for the load, a properly rated PDU, and no daisy-chaining. Have a licensed electrician sign off the design before energising anything.

Three-phase 208 V service is the usual choice above a handful of machines because it balances load across phases and reduces conductor cost. A 200 A three-phase service supports roughly twenty full-size air-cooled machines at full load with sensible headroom.

Air-cooled machines in this class run at 72-82 dB and exhaust essentially all consumed power as heat. That combination decides where the machine can live long before any performance consideration does.

Hydro and immersion variants move the noise problem to a pump and a radiator that can be sited elsewhere, and they make heat reuse practical — space heating, greenhouses and process water are all real deployments we have supported.

Set the machine up on a wired connection with a static lease, configure at least two pool endpoints for failover, and enable alerting on hashrate drop and temperature. Those three steps prevent most of the revenue loss that small operators experience in their first year.

Record baseline hashrate and per-board temperatures the week the machine arrives. Every future diagnosis is a comparison against that baseline, and having it makes board failure obvious weeks before the machine drops offline.

The failure mode in this market is almost never the hardware — it is the transaction. Insist on a named legal entity, a verifiable phone number, a written warranty term, an invoice issued before funds move, serial numbers photographed on the machines you are actually buying, and a test report showing hashrate and per-board temperatures from a real bench run.

Every machine referenced here is listed on our catalogue with a live price, a bench-test report and a photograph of the actual unit, so you can move from this guide to a checkout in two clicks. Crypto, CashApp, Chime and bank transfer are all accepted, and orders ship worldwide from our Hong Kong warehouse to the USA, Canada, Europe, Asia, the Middle East, Latin America and Australia.

We ship air freight via DHL and FedEx with full commercial invoices, HS codes and, where relevant, EORI and VAT documentation for EU and UK buyers. Typical door-to-door transit is three to seven business days to North America and Europe, with sea freight available for container-scale orders where the freight saving justifies the longer timeline.

Deployment support does not stop at delivery. Send us your panel schedule, ambient conditions and pool preference and we will return a circuit plan, a firmware recommendation and a monitoring configuration so the fleet earns from the first day rather than the second week.