Antminer T21 Review 2026: Best Value Current-Gen Miner? Performance, Efficiency & Profitability

The T21: Where Smart Money Meets Smart Mining

Every generation of Bitmain hardware follows the same playbook: launch the flagship S-series at a premium, then follow up with the T-series — same generation silicon, slightly lower binning, significantly lower price. The Antminer S19 had the T19. The S17 had the T17. And the S21 has the T21. History shows that the T-series machines are often the most strategically sound purchases in Bitcoin mining — and the T21 might be the best example yet.

The Antminer T21 delivers 190 TH/s at 19 J/TH using the same BM1368 chip found in the S21. It draws 3,610W, costs meaningfully less than its S-series sibling, and shares the same chassis, cooling architecture, and build platform. For miners operating on tight margins — which, post-halving, means most of us — the T21 represents a fascinating value proposition: nearly identical hardware at a lower price per unit, with only modest concessions in hashrate and efficiency.

At D-Central Technologies, we have been repairing, modifying, and deploying Antminer hardware since 2016. We have opened up T21 units, benchmarked them against S21s running side by side, flashed third-party firmware, and converted them into space heaters for Canadian winters. This review reflects that hands-on experience — not a spec sheet from Bitmain, but a real-world assessment from Mining Hackers who know every solder joint inside these machines.

Whether you are a home miner calculating post-halving breakeven, a small operator optimizing fleet cost per terahash, or a Canadian pleb miner looking to heat your workshop while stacking sats, this is the honest review you need before putting money on the table.

Antminer T21: Complete Specifications

Here is the full specification sheet for the Bitmain Antminer T21. These are Bitmain’s published numbers — and we will tell you exactly how they hold up in our testing below.

The headline here is the BM1368 chip — the same 5nm silicon that powers the flagship S21. The T21 runs 324 of these chips across three hashboards (108 per board, organized into 12 domains each), compared to the S21’s 396 chips (132 per board). Fewer chips means lower total hashrate and slightly reduced efficiency, but the fundamental silicon is identical. This is critical: you are not getting an inferior chip generation. You are getting fewer chips of the same generation.

One specification that deserves special attention: the standard T21 ships configured for 380–415V three-phase power. This is different from the S21, which operates on 200–240V single-phase. For home miners, this is a significant consideration — you will need either a three-phase power connection (uncommon in North American residential) or a modified single-phase conversion setup. We will cover the home mining implications in detail below.

The T21 also supports two operating modes: Normal Energy Mode (NEM) at 190 TH/s and 3,610W, and High Energy Mode (HEM) that pushes the machine to approximately 233 TH/s at 5,126–5,615W. HEM trades efficiency for raw hashrate — dropping from 19 J/TH to roughly 22–24 J/TH. Whether HEM makes sense depends entirely on your electricity cost, and we will run those numbers in the profitability section.

T21 vs S21: The Comparison That Matters

This is the comparison every buyer is making, so let us lay it out clearly. The T21 and S21 share the same generation silicon but differ in binning, chip count, and price. Here is how they stack up:

The performance gap between the T21 and S21 is smaller than most buyers expect. The S21 delivers 5.3% more hashrate at 8.6% better efficiency. In absolute terms, that is 10 TH/s more hashpower and 1.5 J/TH better efficiency. These are not trivial differences at scale — 100 machines would mean 1,000 TH/s more from an S21 fleet — but for a single-unit home miner, the practical impact on daily revenue is modest.

The real question is whether the price premium for the S21 is justified by the performance delta. If the S21 costs 20–30% more than the T21 for only 5.3% more hashrate, the T21 wins on price-per-terahash every time. This is where the T21 earns its reputation as the smart money miner.

One area where the S21 has a clear advantage for home miners: voltage compatibility. The S21 runs on standard single-phase 200–240V power, which is readily available in North American homes. The T21’s stock configuration requires 380–415V three-phase power. This does not mean the T21 cannot be used at home — modified configurations and PDU setups exist — but it adds complexity and cost to a home installation. If plug-and-play simplicity matters to you, the S21 is the easier path. If you are comfortable with electrical modifications or have three-phase power available, the T21 becomes very compelling.

For a deeper comparison including the S21 Pro, see our Antminer S21 Pro Review, which benchmarks all three machines in the S21 generation.

Build Quality and Design

The T21 uses Bitmain’s classic extruded aluminum chassis — the same general design language as the S21. Open it up and you find three hashboards arranged vertically, each carrying 108 BM1368 chips organized into 12 voltage domains. The control board sits behind a removable panel with the familiar Ethernet port, IP report button, reset button, bi-color status LED, and micro-USB port for diagnostics.

Build quality is solid. Bitmain has refined this chassis design over multiple generations, and the T21 benefits from all that iteration. The heatsink assemblies use aluminum fins with spring-loaded screws that distribute even pressure across the chip packages — a design that reduces hot spots and improves long-term reliability. We appreciate this detail: uneven heatsink pressure is one of the most common causes of premature chip failure that we see in our ASIC repair shop.

One detail Braiins noted in their teardown: the T21 uses blue thermal paste, whereas the S21 uses pink. This is a cosmetic difference — both are adequate thermal interface compounds — but it makes it easy to identify which board came from which machine if you are working with mixed inventory.

The fan assemblies are robust. Four high-performance fans rated at 12V DC, 4.5A each (54W per fan, 216W total for all four) provide strong airflow through the heatsink channels. The 4-pin ATX fan connector reflects the higher current draw of these fans compared to previous generations. These are not quiet fans — they are engineered for thermal performance in data center environments — but they are well-balanced and should not develop bearing noise prematurely under normal operating conditions.

Each BM1368 chip has its own individual temperature sensor, a significant improvement over previous generations where temperature monitoring was more coarse-grained. This per-chip thermal visibility is valuable both for automated thermal protection and for diagnostics — if one chip starts running hot, you can identify it precisely rather than guessing which chip on a domain is the problem.

Overall, the T21’s build quality is on par with the S21. You are not getting a downgraded chassis or cheaper components. The cost savings come from fewer chips per hashboard, not from cutting corners on construction.

Performance Benchmarks

In our testing, the T21 delivers consistent performance at its rated specifications. Here is what we recorded over an extended test window at 25°C ambient temperature in Normal Energy Mode:

Temperature Impact on Performance

Like all ASIC miners, the T21’s performance varies with ambient temperature. Here is how different environments affect the machine:

The takeaway for Canadian miners: cold climate is a genuine advantage. At 5°C ambient — a typical unheated garage in a Canadian winter — the T21 runs at full rated hashrate with fans barely above idle. Less fan wear, less noise, and maximum performance. This is one of the reasons we at D-Central are bullish on home mining in Canada: our climate is a competitive edge that cannot be replicated by data centers in Texas or the Middle East.

The thermal throttle threshold kicks in when chip temperatures exceed roughly 80°C. At that point, the control board reduces clock frequencies to prevent damage. If your ambient temperature regularly exceeds 35°C and you do not have active ventilation, expect reduced hashrate and increased wear on components. See our most efficient Bitcoin miners ranking for how the T21 compares to other models at different operating conditions.

Noise and Thermal Output

There is no sugarcoating this: the T21 is loud. At approximately 75 dB under normal operating conditions at 25°C, it is comparable to standing next to a vacuum cleaner running continuously. This is standard for current-generation ASIC miners — the S21 produces similar noise levels — but it makes untreated indoor operation impractical for living spaces.

Noise Management Options

• Dedicated room: The most common approach. A basement, garage, or outbuilding with a solid door between you and the machine. Add exhaust ducting to vent the hot air outside.
• Shroud and duct setup: D-Central’s duct shroud adapters connect to standard 8-inch round ductwork, directing noise and heat to where you want them (outside in summer, into your home in winter).
• Sound enclosure: Purpose-built sound boxes can reduce perceived noise by 20–30 dB. Combined with ducting, this brings the T21 into the 45–55 dB range — comparable to a loud conversation. See our ASIC Noise Reduction Guide for detailed instructions.
• Fan replacement: Aftermarket low-noise fans (such as Noctua industrial models) can significantly reduce noise but require careful thermal management — reduced airflow means higher chip temperatures.

Heat Output: The Dual-Purpose Opportunity

The T21 consumes 3,610W of electrical power. Virtually all of that energy converts to heat. That translates to approximately 12,300 BTU/hr of thermal output — equivalent to a high-output portable space heater.

For perspective:

• A typical 1,500W household space heater produces ~5,100 BTU/hr
• The T21 produces ~12,300 BTU/hr — enough to heat a 400–600 sq ft space in moderate climates
• In a well-insulated Canadian home, a T21 can meaningfully offset your furnace load during winter months

This dual-purpose capability — mining Bitcoin while heating your home — is central to the D-Central philosophy. You are going to heat your house anyway. Why not stack sats while you do it? The T21 is particularly compelling for this use case because it offers nearly the same heat output as the S21 (which produces ~11,945 BTU/hr) at a lower purchase price. Same warmth, lower entry cost.

For more on converting miners into dedicated heating solutions, see our Bitcoin Space Heaters collection.

Firmware Compatibility: Unlocking the T21’s Full Potential

One of the most important factors in any ASIC purchase is third-party firmware support. Custom firmware can dramatically change a miner’s economics — enabling autotuning, undervolting, overclocking, and advanced monitoring that stock firmware simply does not offer. The T21 has strong support across all three major firmware platforms:

Braiins OS+

Braiins OS+ fully supports the T21. Key features include:

• Autotuning: Automatically finds the optimal frequency and voltage for each individual chip, maximizing efficiency
• Power targeting: Set a specific wattage target and let the firmware optimize hashrate within that power budget — excellent for operators on limited circuits
• Stratum V2: Support for the next-generation mining protocol, which improves efficiency and decentralization
• Per-chip optimization: The T21’s individual chip temperature sensors pair exceptionally well with Braiins autotuning

With Braiins autotuning, we have seen T21 units achieve 18.2–18.5 J/TH efficiency — a meaningful improvement over the stock 19.0 J/TH. On a miner running 24/7, that efficiency gain compounds into real savings.

VNish Firmware

VNish supports the T21 (including both Amlogic and Cvitek control board variants as well as BHB68703). Features include:

• Overclocking profiles: Push beyond stock hashrate with managed thermal limits
• Undervolting: Reduce power consumption for improved efficiency — particularly valuable during high-difficulty periods
• Auto-restart and watchdog: Improved uptime management compared to stock firmware
• Multi-pool management: More sophisticated failover and load-balancing options

LuxOS

LuxOS (by Luxor Technology) has added T21 support, including the BHB68703 control board variant. Notable features:

• Power targeting: Similar to Braiins, set a wattage ceiling and optimize within it
• Fleet management: Centralized dashboard for multi-unit deployments
• Curtailment API: Programmatic power reduction for demand-response programs — increasingly relevant as miners participate in grid services

Important Note on Control Board Variants

The T21 shipped with different control board variants across production batches. Before flashing any custom firmware, verify your specific control board model (check the label on the board itself or the web interface’s system information page). All three firmware vendors maintain compatibility lists for specific board revisions. Installing firmware for the wrong board variant can brick your control board.

For detailed firmware installation procedures, see our Antminer Firmware Update Guide — it covers every model and every method.

Profitability Analysis

Let us talk numbers. Profitability depends on three variables: hashrate, electricity cost, and Bitcoin price. We cannot predict Bitcoin’s price, but we can model the T21’s economics at various electricity rates. The following analysis uses the T21 at stock NEM settings (190 TH/s, 3,610W) and current network conditions.

Daily Revenue and Costs at Different Electricity Rates

At current Bitcoin prices and network difficulty, the T21 generates approximately $6–$8 USD in daily mining revenue (this fluctuates with difficulty adjustments and BTC price). The machine is profitable at electricity rates below approximately $0.08–0.10/kWh in pure mining terms. Above that threshold, the dual-purpose heating value proposition becomes essential to justify operation.

For real-time profitability estimates with current network conditions, use our Mining Profitability Calculator.

T21 vs S21 ROI Comparison

The break-even comparison between the T21 and S21 is more nuanced than most reviews acknowledge. Consider this scenario:

• If the T21 costs 20% less than the S21 but produces only 5.3% less hashrate, the T21 reaches break-even faster
• The S21’s better efficiency (17.5 vs 19.0 J/TH) means lower operating costs, which compounds over time
• At very low electricity costs ($0.04/kWh), the efficiency advantage is less significant — the lower purchase price dominates the ROI calculation
• At higher electricity costs ($0.10+/kWh), the S21’s efficiency advantage becomes more meaningful — lower operating cost per terahash extends the profitable life of the machine

Rule of thumb: If your electricity is cheap and you are optimizing for fastest ROI, buy the T21. If your electricity is expensive and you are optimizing for the longest profitable runway, the S21’s efficiency premium is worth paying for. If your electricity is very expensive ($0.12+/kWh), neither machine works without heat offset value — and the T21’s lower purchase price makes it the smarter space heater purchase.

For detailed comparisons across all current-generation miners, see our Best Bitcoin Miners by Budget guide.

The Value Proposition: When the T21 Beats Everything

The T21’s value proposition comes down to one metric: price per terahash. This is the number that matters for fleet economics, and the T21 consistently offers one of the best $/TH ratios in the current generation.

Here is the framework for when the T21 is the right choice:

• Budget-constrained expansion: You have a fixed capital budget and want to maximize total hashrate. Two T21s may deliver more total TH/s than one S21 Pro for similar money.
• Cheap electricity: At $0.04–0.06/kWh, the efficiency gap between 19 J/TH and 17.5 J/TH is worth only $1–2/day. The lower purchase price pays for itself long before the efficiency difference catches up.
• Heat recovery applications: You are buying a miner to heat your home. The T21 produces 12,300 BTU/hr — nearly identical to the S21’s 11,945 BTU/hr. Same heat, lower price. The T21 is the rational space heater miner.
• Fleet diversification: Running a mix of T21s and S21s lets you optimize your fleet economics across varying power conditions.
• Short time horizon: If you plan to sell or upgrade within 12–18 months, the T21’s faster break-even matters more than the S21’s long-term efficiency advantage.

When should you pay more for the S21 instead?

• Expensive electricity ($0.10+/kWh): The S21’s 8.6% efficiency advantage compounds significantly at higher electricity costs.
• Space-constrained deployments: If you have limited rack space or circuit capacity, the S21 delivers more hashrate per unit.
• Home mining simplicity: The S21 runs on standard 200–240V single-phase power without modification. The T21 requires either three-phase power or a conversion setup.
• Long holding period: If you plan to run the machine for 3+ years, the S21’s better efficiency extends its profitable lifespan further into future difficulty increases.

Home Mining Considerations

The T21 can absolutely be used for home mining, but it requires more preparation than the S21 due to its power configuration.

Power Requirements

The standard T21 ships configured for 380–415V three-phase power. Most North American homes have single-phase 120/240V service. This creates three paths for home miners:

1. Three-phase power (if available): Some rural properties, workshops, and commercial spaces have three-phase service. If you already have it, the T21 plugs right in. Budget $0 for electrical work.
2. Single-phase 200V/240V conversion: Third-party vendors (including some bundles available through retailers) offer the T21 with a PDU (Power Distribution Unit) configured for single-phase 200V operation. This is the most common home mining approach. The PDU handles the voltage conversion, and the T21 connects to a standard 240V, 30A circuit. Budget $200–$500 for the PDU and installation.
3. APW12 PSU swap: Some operators replace the stock PSU with an APW12 configured for single-phase 240V. This typically results in a derated hashrate (~170 TH/s at 3,230W) because the APW12 cannot deliver enough power for full-speed operation. This is a viable option if you want lower power draw and are comfortable with reduced hashrate. Caution: Running the APW12 at its limits can damage the PSU — do not attempt to run full hashrate on an APW12.

Minimum circuit requirements for home operation:

• 240V / 20A dedicated circuit (NEMA 6-20 or L6-20) — tight but workable for NEM mode
• 240V / 30A dedicated circuit (NEMA L6-30) — recommended, provides headroom
• All wiring should be 10 AWG copper minimum for 20A circuits, 8 AWG for 30A
• Dedicated breaker — never share a circuit with other equipment
• Have a licensed electrician install the circuit if you do not have one available

Ventilation and Heat Management

At 12,300 BTU/hr, the T21 will turn any enclosed space into a sauna within minutes if you do not manage airflow. For home installations:

• Winter: Duct the exhaust heat into your living space. The T21 replaces approximately 3.6 kW of electric heating — which is exactly what it consumes. Your net heating cost is the same, but you are also mining Bitcoin. This is the core of the Bitcoin Space Heater concept.
• Summer: Duct the exhaust outside. The miner’s heat becomes a liability when you are already running air conditioning. Some operators shut down during peak summer months or move the miner to a well-ventilated garage or shed.
• Year-round: An insulated outbuilding or garage with intake and exhaust ducting provides the best balance. Fresh cold air in (Canadian climate advantage), hot air out or redirected as needed.

Space Heater Conversion: The T21’s Hidden Strength

This is where the T21 arguably makes more sense than any other miner in the S21 family. Here is the logic:

1. The T21 produces approximately 12,300 BTU/hr of heat — comparable to the S21’s 11,945 BTU/hr
2. The T21 costs significantly less than the S21
3. In a space heater application, efficiency (J/TH) matters less because the “waste” heat is the primary product
4. You are heating your home either way — the T21 lets you do it while mining Bitcoin at the lowest capital cost

At D-Central, we have pioneered Bitcoin space heater conversions since the S9 era. The T21 is an excellent candidate for this treatment. Our conversion process includes exhaust shrouding, duct adaptation, noise reduction, and integration with your home’s heating layout. The result is a mining unit that replaces a portion of your heating system while generating Bitcoin revenue.

For regions with cheap electricity — Quebec at $0.06 CAD/kWh, Manitoba at similar rates, or US states like Washington and Idaho — the T21 space heater makes exceptional economic sense. You were going to spend money on heating fuel or electricity regardless. The T21 converts that heating expense into Bitcoin mining, effectively reducing your cost basis to near zero.

Explore our full range of Bitcoin Space Heater editions to see how we build these conversions.

Common Issues and Repair

The T21 shares the BM1368 chip platform and much of its board design with the S21, which means the failure modes and repair procedures are closely related. Here are the most common issues we see in our repair shop:

Temperature Sensor Failures

The per-chip temperature sensors on the T21 are a double-edged sword. They provide excellent thermal visibility, but a failed sensor can cause the control board to misread chip temperatures, leading to unnecessary throttling or shutdown. Symptoms include the miner reporting abnormally high or low temperatures on specific chips, or hashboards failing to start. Check the inlet and outlet temperature sensor components (U4, U5) and adjacent SMD components for cold solder joints.

Hashboard Detection Issues

The most common support ticket: one or more hashboards not detected at startup. The usual suspects are:

• Ribbon cable connections: Shipping vibration can partially unseat the hashboard-to-control-board ribbon cables. Reseat all connections firmly.
• Domain voltage issues: If chip detection is incomplete (some chips missing on a hashboard), check the voltage in the affected domain. Test points should read 1.2V and 0.8V. Deviation indicates a failed LDO voltage regulator or a shorted ASIC chip.
• BM1368 chip failures: Individual chip failures can take down an entire domain (9 chips). Diagnosis requires a multimeter or dedicated BM1368 chip tester. Replacement requires precision BGA rework equipment.

PSU-Related Issues

The external PSU is a separate failure point. Symptoms include the miner not powering on, intermittent shutdowns, or reduced hashrate due to insufficient power delivery. If you suspect PSU issues, test with a known-good power supply before assuming a hashboard problem.

Fan Failures

The four high-draw fans (4.5A each) are robust but will eventually wear out. A failed fan triggers thermal protection, which reduces hashrate or shuts down the machine entirely. Replacement fans are readily available, and the swap is straightforward — four screws and a connector.

D-Central’s T21 Repair Capabilities

At D-Central, we carry the full range of T21/S21 repair components: BM1368 chips (all variants — PB, PA, PM, PV, AA), temperature sensor chips, LDO regulators, op-amp modules, capacitors, and resistors. Our technicians have repaired hundreds of BM1368-based hashboards and understand the specific failure patterns of this chip generation.

If your T21 has a hashboard issue, contact our ASIC repair team. We offer diagnostics, component-level repair, and full hashboard testing before return. Our turnaround time for T21 repairs is typically 5–10 business days depending on parts availability and repair complexity.

Frequently Asked Questions

Verdict: The Smart Money Miner

The Antminer T21 is not the fastest miner you can buy. It is not the most efficient. But it might be the smartest purchase in the current generation, and here is why:

The T21 delivers 95% of the S21’s performance at a meaningfully lower price. It uses the same BM1368 silicon, the same chassis design, and supports the same third-party firmware ecosystem. The 10 TH/s hashrate gap and 1.5 J/TH efficiency gap are real, but they are small enough that the purchase price difference often makes the T21 the better ROI bet — especially for operators with cheap electricity or those using heat recovery.

Scores

Who Should Buy the T21?

• Budget-conscious miners who want current-gen BM1368 silicon without paying the S21 premium
• Space heater operators who prioritize heat output per dollar spent
• Operators with cheap electricity ($0.04–0.08/kWh) where the efficiency gap matters less
• Fleet builders who want to maximize total terahash per dollar of capital
• Miners with three-phase power who can take advantage of the stock power configuration

Who Should Consider the S21 Instead?

• Home miners without three-phase power who want a simpler installation
• Operators paying $0.10+/kWh where the S21’s efficiency advantage compounds significantly
• Miners planning to hold for 3+ years where long-term efficiency extends profitable operation

The T21 is not a compromise. It is a strategic choice. Bitmain positioned it as the value option, and it delivers exactly that — current-generation performance at a price point that accelerates your ROI. In a post-halving world where margins are tight and every sat matters, that is not just smart mining. That is Mining Hacker thinking.

Ready to start mining? Browse our full selection of miners, parts, and accessories at D-Central Technologies. Need help choosing the right machine for your setup? Contact our team — we have been matching miners with the right hardware since 2016.