Bitmain Antminer S21 Pro review
The default pick for buyers with cheap power: 234 TH/s air-cooled at 15 J/TH, and roughly $16 to $24 per terahash as of August 2026.
Bitmain Antminer S21 Pro specifications
- Manufacturer
- Bitmain
- Released
- October 2024
- Hashrate
- 220-245 TH/s (234 TH/s typical)
- Power draw
- 3,510 W
- Efficiency
- 15.0 J/TH
- Electricity per day
- 84.2 kWh
- Cooling
- Air
- Noise
- 75 dB
- Algorithm
- SHA-256
- Estimated price
- $3,800 to $5,500
- Best for
- Most buyers: the strongest balance of price, hashrate and efficiency in an air-cooled unit
Hashrate as sold: 220-245 TH/s (234 TH/s typical). The comparison table uses the nominal 234 TH/s rating.
Should you buy the Bitmain Antminer S21 Pro?
If you are going to buy exactly one miner and then stop comparing spec sheets, the Antminer S21 Pro is where that decision usually ends. It hashes 234 TH/s on plain air cooling at 3510 W, which works out to 15.0 J/TH, and as of August 2026 it sells for $3,800 to $5,500. Divide price by hashrate and you get roughly $16 to $24 per terahash, the number that matters more than any headline spec when you are deciding what to spend on.
The payback math splits cleanly on electricity. At $0.04 per kWh industrial power the S21 Pro earns roughly $10 to $15 a day as of mid 2026, which clears the low end of the price band in about nine months and the high end in about eighteen, assuming price and difficulty hold, which they never exactly do. At $0.10 per kWh, a typical American home rate, the same machine loses about $8 a day per ASIC Miner Value, and payback never arrives at all.
That split is the whole verdict. Network hashrate sits near 910 EH/s as of August 2026, down roughly 19 percent from the November 2025 peak of 1,108 EH/s, which has given this class of hardware some breathing room. If your power costs less than about $0.08 per kWh and you have somewhere to put 75 dB of fan noise, the S21 Pro is the machine to measure everything else against. If you do not, no discount on the hardware will fix the electricity bill.
Pros and cons
What works
- 15.0 J/TH efficiency from plain air cooling, with no immersion tank or hydro plumbing to buy or maintain
- Roughly $16 to $24 per terahash across the $3,800 to $5,500 price band as of August 2026
- Earns roughly $10 to $15 a day at $0.04/kWh industrial rates as of mid 2026
- Payback in roughly 9 to 18 months at industrial power rates, depending on which end of the price band you pay
- Shipping since October 2024, so it is a known quantity rather than a first batch gamble
What to watch
- Loses about $8 a day at $0.10/kWh as of mid 2026, so most home buyers never reach payback at all
- 3510 W is more than a standard household outlet circuit can supply, so it needs dedicated wiring
- 75 dB of fan noise rules out any shared living space
- Rated 234 TH/s typical, but batches ship anywhere from 220 to 245 TH/s, so your unit may hash below the calculator number
How the Bitmain Antminer S21 Pro compares
Frequently asked questions
How loud is the Antminer S21 Pro?
It runs at about 75 dB, roughly a vacuum cleaner that never switches off. That is too loud for any room people spend time in, so plan on a garage, shed, or soundproofed enclosure, and remember that any enclosure still has to move about 3510 W of heat out of the box.
How much electricity does the S21 Pro use per day?
About 84.2 kWh per day from its constant 3510 W draw. At $0.10 per kWh that is 84.2 x 0.10, about $8.42 a day and roughly $253 a month, before the machine earns anything. At $0.04 per kWh the same 84.2 kWh costs about $3.37 a day.
Is the S21 Pro profitable at home electricity rates?
Usually not. Above roughly $0.08 per kWh the math stops working: at a typical US home rate of $0.10 per kWh, ASIC Miner Value showed it losing about $8 a day as of mid 2026. It only makes sense on industrial or similarly cheap power near $0.04 per kWh, where it earns roughly $10 to $15 a day.
Why do S21 Pro listings show different hashrates?
Because Bitmain ships it in batches rated anywhere from 220 to 245 TH/s, with 234 TH/s the typical figure. Check the exact rating on the listing before paying, since a 220 TH/s unit at the same price costs about 6 percent more per terahash than a 234 TH/s one.