Product Overview

The Bitmain Antminer S21 Pro 245Th is the highest-performance air-cooled variant in Bitmain’s S21 Pro series — a flagship-class Bitcoin (BTC) SHA-256 ASIC miner that delivers 245 terahashes per second at approximately 15.5 J/TH efficiency. It sits at the pinnacle of Bitmain’s current-generation air-cooled Bitcoin mining hardware, offering exceptional energy efficiency without requiring the hydro-cooling infrastructure of the S21 Hydro or S21 XP Hydro series.

The S21 Pro series represents a significant step forward from the S19 generation, leveraging Bitmain’s advanced 5nm chip architecture to achieve sub-16 J/TH efficiency — a level that substantially improves the economics of Bitcoin mining compared to older hardware. At 245 TH/s, the S21 Pro 245Th is among the most powerful air-cooled Bitcoin miners available, delivering maximum hashrate contribution per rack slot in a standard mining farm configuration.

For South African operators with commercial or industrial power infrastructure, the S21 Pro 245Th represents state-of-the-art Bitcoin mining hardware that maximises both hashrate output and efficiency from each deployed unit. Its ~3800W power draw requires serious electrical planning but offers best-in-class J/TH performance in the air-cooled ASIC segment.

Key Features

• 245 TH/s hashrate: Bitmain’s highest-output air-cooled Bitcoin miner in the S21 Pro series, delivering maximum SHA-256 hashrate per rack unit deployed.
• ~15.5 J/TH efficiency: At approximately 3800W, the S21 Pro 245Th achieves roughly 15.5 J/TH — significantly better than S19-era hardware (23–29 J/TH) and competitive with the best air-cooled miners currently available.
• Air-cooled design — no hydro required: Despite its exceptional efficiency, the S21 Pro 245Th uses standard air-cooling with high-speed fans. No hydro loop, pump, radiator, or specialist cooling infrastructure is required.
• SHA-256d algorithm: Mines Bitcoin (BTC) as the primary target. Also compatible with Bitcoin Cash (BCH) and Bitcoin SV (BSV).
• Bitmain’s flagship air-cooled generation: The S21 Pro represents the peak of Bitmain’s 5nm air-cooled Bitcoin mining hardware. Standard Antminer management interface, firmware, and support ecosystem.
• Ethernet (RJ-45) connectivity: Single wired network port. Web interface for pool configuration and monitoring.
• Maximum hash density per rack: At 245 TH/s per unit, operators need fewer machines to achieve a target total hashrate versus previous generations, reducing infrastructure complexity and management overhead.

Technical Specifications

• Algorithm: SHA-256d
• Supported coins: Bitcoin (BTC), Bitcoin Cash (BCH), Bitcoin SV (BSV)
• Hashrate: 245 TH/s (±3%)
• Power consumption: ~3800W (±5%) at 25°C ambient
• Power efficiency: ~15.5 J/TH (±5%)
• Cooling type: Air-cooled, dual high-speed fans
• Noise level: ~75 dB(A)
• Input voltage: 200–240V AC
• Networking: Ethernet (RJ-45)
• Operating temperature: 5°C to 40°C
• Dimensions (L×W×H): 400 × 195 × 290 mm
• Net weight: ~16 kg

Power & Installation Notes

South Africa’s 230V/50Hz supply is within the Antminer S21 Pro 245Th’s 200–240V input range. No voltage converter is required.

At approximately 3800W continuous draw, the S21 Pro 245Th is one of the higher-wattage air-cooled miners in this catalogue. A dedicated 32A circuit, installed by a registered electrician, is required for single-unit operation. For farms with multiple S21 Pro units, a dedicated distribution board with individual circuit breakers per miner and appropriate cable sizing for sustained 3.8kW loads per circuit is essential. Engage a qualified industrial electrician for multi-unit installations.

Load shedding at 3.8 kW is a significant operational challenge for South African mining operations. A 10kWh residential battery provides approximately 2.6 hours of runtime at full load. For continuous 24/7 operation — which is necessary to maximise the value of premium hardware like the S21 Pro — a generator or commercial-grade backup power system is required. Factor in load shedding schedules and backup power costs when calculating the total operating cost.

Thermal management: the S21 Pro 245Th generates substantial heat. Ensure minimum 200–300mm clearance at inlet and exhaust fan faces, active air extraction from the mining space, and ambient temperature maintained below 40°C. In South Africa’s warmer climates, active cooling (air conditioning or evaporative systems) in enclosed rooms is often necessary.

Electricity Cost Context — South Africa

Running the Antminer S21 Pro 245Th at 3800W continuously consumes approximately 91.2 kWh per day, or roughly 2 736 kWh per month. At R2.80/kWh (reference residential tariff — municipal rates vary), the estimated monthly electricity cost is approximately R7 661 per month.

Calculation: (3800 ÷ 1000) × 24 × 30 × R2.80 = ~R7 661/month.

At standard South African residential tariffs, this represents a substantial operating cost. The S21 Pro 245Th is best suited to operations with commercial or industrial electricity rates. However, its 15.5 J/TH efficiency means it produces more Bitcoin per rand of electricity than almost any other air-cooled miner available — which is the key metric that justifies the operating cost at appropriate scale. This is a cost estimate only and does not represent a profitability projection.

Ideal Use Cases

• Commercial and industrial Bitcoin mining operations: Operators running 10+ units in purpose-built facilities with commercial power supply and thermal management infrastructure.
• Maximising hashrate density per rack slot: At 245 TH/s, the S21 Pro delivers the highest air-cooled Bitcoin hashrate per machine, maximising output from limited rack space.
• Replacing S19-era hardware: A direct upgrade from S19k Pro, S19J Pro+, or T21-class hardware, delivering approximately 35–50% better efficiency in the same rack footprint.
• Premium fleet standardisation: Operators who want to build their entire Bitcoin mining fleet on state-of-the-art 5nm hardware for maximum long-term competitive efficiency.
• Operators avoiding hydro complexity: For operators who want S21-generation efficiency without investing in hydro cooling infrastructure — the S21 Pro 245Th delivers near-hydro efficiency in a standard air-cooled package. See also the Antminer S21 Pro 234Th for a slightly lower-cost variant.

Frequently Asked Questions

Does the Antminer S21 Pro 245Th work on South African power?
Yes. SA’s 230V/50Hz supply is within the S21 Pro’s input range. A dedicated 32A circuit from a registered electrician is required. At 3.8 kW, this is one of the higher-wattage miners in our catalogue — electrical planning is critical.

How does the S21 Pro 245Th compare to the S21 Pro 234Th?
The 245Th variant delivers 11 TH/s more output at the same efficiency class (~15–15.5 J/TH), making it the top-performing air-cooled S21 Pro. The 234Th offers slightly lower cost for marginally less hashrate. See: Bitmain Antminer S21 Pro 234Th.

What Bitcoin mining pools are compatible with the S21 Pro 245Th?
All major SHA-256 Bitcoin pools: Foundry USA Pool, AntPool, F2Pool, ViaBTC, Braiins Pool. Configuration is standard via the Antminer web interface.

Why choose air-cooled S21 Pro over the S21 XP Hydro?
The S21 XP Hydro series offers even better efficiency (~13 J/TH) but requires hydro cooling infrastructure (pump, radiator, coolant loop, plumbing). The S21 Pro 245Th delivers excellent efficiency without that infrastructure overhead — ideal for operators in standard air-cooled farm setups.

How does load shedding affect the S21 Pro 245Th’s economics?
South Africa’s load shedding reduces effective operating hours per day. At stage 6 (8+ hours/day of shedding), effective uptime drops to ~66%. This significantly impacts daily BTC output. Operators should factor local shedding schedules and backup power costs into their operational modelling.

What’s Included

• 1× Bitmain Antminer S21 Pro 245Th ASIC miner unit
• Integrated or bundled PSU (confirm with order — S21 Pro typically includes integrated PSU)
• Power cable (region-specific — South African plug may require local adaptor or electrician wiring)
• Ethernet cable not included
• Quick-start guide