Bitmain Antminer S21+ (235Th)

The Bitmain Antminer S21+ is the volume deployment model in the current S21 family. Released in February 2025, it delivers 235 TH/s at 3,875W and 16.49 J/TH from Bitmain's BM1370 5nm chip architecture. Not the most efficient S21 variant. Not the cheapest per unit either. But consistently the best value when the question is "how much total hashrate can I deploy for a fixed hardware budget?"

The S21 family now spans five air cooled tiers. The original S21 at 200 TH/s and 17.5 J/TH is the legacy model, efficient enough to operate but increasingly outpaced. The S21+ at 235 TH/s and 16.49 J/TH is the mid range workhorse released in February 2025. The S21 Pro at 234 TH/s and 15.0 J/TH targets operators who prioritize efficiency over hashrate volume. The S21 XP at 270 TH/s and 13.5 J/TH is the air cooled efficiency leader. And the S21 XP Hydro at 473 TH/s and 12.0 J/TH adds liquid cooling for maximum density. The S21+ occupies the value tier: it costs less per unit than the Pro, XP, or any hydro variant, but delivers enough performance to stay competitive in fleet deployments.

Fleet math is where the S21+ earns its place. A capital constrained operation with $100,000 to spend can deploy meaningfully more total hashrate in S21+ units than in S21 XP or S23 units at current market pricing. Ten S21+ miners produce 2,350 TH/s. That same budget might buy six S23 units producing 1,908 TH/s. The S21+ fleet mines more total Bitcoin per day because it has more total hashrate pointed at the network, even though each individual unit spends more electricity per terahash than the S23.

The catch is your electricity rate. Every J/TH of efficiency difference between the S21+ and a more efficient competitor translates into real daily electricity cost. At $0.03 per kWh (hydropower, stranded gas, subsidized industrial tariffs), the gap between 16.49 J/TH and 13.5 J/TH costs roughly $1.50 per day per unit in extra electricity. Barely noticeable against the additional Bitcoin production from higher fleet hashrate. At $0.08 per kWh urban commercial power, that same gap costs approximately $4 per day per unit and compounds painfully across a 10 unit fleet. The S21+ is the right machine for cheap power environments where capital efficiency trumps operating efficiency.

Universal 100 to 240V input provides genuine global deployment flexibility. At 220V the S21+ draws approximately 17.6 amps, fitting most commercial circuits. At 110V it draws about 35.2 amps, requiring a dedicated 40 amp circuit but remaining deployable in North American residential settings with proper electrical setup. 75 dB air cooled noise from four fans is standard industrial ASIC volume: not suitable for shared living spaces but entirely normal for garages, basements, dedicated mining rooms, and hosting facilities.

400 x 195 x 290 mm at 15.1 kg in the standard Antminer chassis means the S21+ shares its physical format with the S21 and S21 XP. Rack layouts, shelving configurations, and ventilation planning designed for one model work for any of them. Bitmain firmware provides the same management interface across the entire Antminer fleet: pool configuration, hashrate monitoring, temperature alerts, and remote management through the web dashboard. Third party firmware options are available for operators who want additional tuning control.

5 to 35 degrees Celsius operating range is tighter than some S21 variants (the XP rates to 45 degrees). Operators in hot climate regions or facilities without climate control should confirm that ambient temperatures stay below 35 degrees during peak summer months. Humidity tolerance runs 5 to 90 percent non condensing.
MillionMiner ships the S21+ brand new with Bitmain warranty, PSU, and power cables included. Free DDP delivery worldwide handles all customs, duties, and import taxes. Hosting at MillionMiner managed facilities is available for operators who want the fleet hashrate advantage without building their own infrastructure.