Antminer S21 XP Hyd Review 2026: 473 TH/s Hydro-Cooled Bitcoin Miner

The Antminer S21 XP Hyd is Bitmain’s answer to a question every serious Bitcoin miner has asked: how do you push SHA-256 efficiency to the absolute edge without burning down your facility? The answer is hydro cooling, BM1370 chips, and 473 TH/s of raw hashpower packed into a unit smaller than most air-cooled miners half its performance.

At D-Central Technologies, we have been tearing apart, rebuilding, and deploying Antminers since 2016. We have seen every generation from the S9 to the S21 Pro. The S21 XP Hyd represents something different: it is the first hydro-cooled unit that makes genuine economic sense for small-to-mid-scale operators, not just industrial farms with unlimited capital. This is our complete, no-nonsense review.

Antminer S21 XP Hyd: Full Specifications

Before we get into the nuances, here is everything you need to know at a glance. These are the official Bitmain specifications, verified against our own benchmarks.

The numbers that matter most: 473 TH/s at 12 J/TH. To put that in perspective, the original Antminer S21 shipped at 200 TH/s with 17.5 J/TH. The XP Hyd delivers 2.36x the hashrate at 31% better efficiency. That is not incremental improvement — that is a generational leap.

Architecture Deep Dive: BM1370 Chips and Hydro Cooling

The BM1370 ASIC Chip

The heart of the S21 XP Hyd is the BM1370, Bitmain’s latest-generation SHA-256 ASIC chip. Each BM1370 delivers over 1.2 TH/s per chip — a substantial improvement over the BM1368 (700+ GH/s per chip) used in the standard S21 and S21 Hyd, and a massive leap from the BM1366 (500 GH/s per chip) in the S19 XP series.

With 324 BM1370 chips distributed across three hashboards (108 chips each), the S21 XP Hyd achieves its 473 TH/s target through sheer density and per-chip efficiency. The BM1370 runs on a refined process node that enables lower voltage operation per transistor, which translates directly into the 12 J/TH wall efficiency rating. For a deeper technical breakdown of Bitmain’s chip evolution, see our Complete Guide to Bitcoin ASIC Chip Evolution: BM1385 to BM1370.

Three Hashboard Configuration

The unit houses three independent hashboards, each carrying 108 BM1370 chips. This modular architecture is critical for serviceability. If a single hashboard fails, you can isolate and replace it without downing the entire unit — something that matters enormously when you are running at nearly half a petahash per machine. If you ever need board-level repair, D-Central’s Antminer S21 XP repair service handles these at the component level.

Integrated Water Block Design

Unlike air-cooled units that rely on heatsinks and high-speed fans to dissipate heat, the S21 XP Hyd uses a direct liquid-to-chip cold plate integrated onto each hashboard. Coolant flows directly over machined copper or aluminum water blocks that make contact with the ASIC packages. The result is dramatically more efficient thermal transfer compared to air cooling — liquid has roughly 25x the thermal conductivity of air.

This is what allows Bitmain to push the BM1370 chips harder while maintaining lower junction temperatures, which extends chip lifespan and reduces thermal throttling to near zero under proper operating conditions.

Hydro Cooling Explained: What You Actually Need

If you have only ever run air-cooled ASICs, hydro cooling introduces a new infrastructure layer. Here is exactly what is involved.

How the Water Loop Works

The S21 XP Hyd connects to an external Coolant Distribution Unit (CDU) via quick-connect water fittings. Hot coolant exits the miner, flows to the CDU where the heat is rejected (typically via a radiator, dry cooler, or heat exchanger), and the cooled liquid is pumped back through the miner in a closed loop.

The system requires:

• Coolant flow rate: 8.0–10.0 L/min per unit
• Maximum coolant pressure: ≤3.5 bar
• Inlet coolant temperature: Ideally 20–35°C for optimal hashrate stability
• Approved coolants: Deionized water, purified water, or glycol-based antifreeze (critical for cold climates like Canada)

CDU (Coolant Distribution Unit) Requirements

The CDU is the external system that manages coolant circulation and heat rejection. You have several options:

• Bitmain’s OEM CDU: Purpose-built for their Hyd series, handles multiple units in a rack
• Third-party CDUs: Industrial liquid cooling distribution units from companies like CoolIT, GRC, or custom-built systems
• DIY heat exchanger setup: For smaller deployments, a high-flow pump, reservoir, and radiator/dry cooler can work — but this requires careful engineering

The key metric is thermal rejection capacity. The S21 XP Hyd produces roughly 5,676W of heat. Your CDU and heat rejection system must handle at least that much thermal load per unit, with headroom for ambient temperature variations. Planning to run 10 units? You need 56+ kW of cooling capacity.

Coolant Chemistry Matters

This is where operators get burned. Tap water will corrode your water blocks within months. Always use:

• Deionized (DI) water with a biocide additive to prevent algae and bacterial growth
• Propylene glycol antifreeze mix (30–50% concentration) if your facility operates in sub-zero ambient temperatures — essential for Canadian operations
• pH monitoring: Maintain coolant pH between 7.0–8.5
• Filtration: Inline particulate filters to prevent sediment from clogging water block micro-channels

For more on liquid cooling fundamentals and how to set up a proper cooling loop, see our Immersion Cooling for Home Bitcoin Miners guide. While immersion and hydro cooling are different technologies, the coolant management principles overlap significantly.

Real-World Performance Analysis

Hashrate Consistency

In our testing and deployment experience, the S21 XP Hyd consistently hits between 460–480 TH/s depending on coolant inlet temperature. With coolant at 25°C inlet, the unit stabilizes around 473 TH/s — right at the rated spec. Push inlet temperature to 35°C and you may see slight derating to around 460 TH/s. Keep it below 20°C (very achievable in Canadian winters) and you can sometimes see the unit hold steady at 478–480 TH/s.

This stability is the hydro advantage. Air-cooled units are sensitive to ambient temperature, dust accumulation, and fan degradation. The S21 XP Hyd maintains a near-flat hashrate curve as long as coolant flow and temperature are within spec.

Power Draw Accuracy

Bitmain rates the S21 XP Hyd at 5,676W ±5% at the wall. In practice, we have measured between 5,500W and 5,900W depending on hashrate variance and input voltage stability. The 12 J/TH efficiency figure holds up under real-world conditions — a remarkable achievement for any ASIC at this hashrate tier.

Note that this power figure does not include CDU power consumption. Your pumps, fans (for dry coolers/radiators), and control systems will add 5–15% to total system power draw depending on your cooling infrastructure. Budget 6,000–6,500W total system power per unit for realistic planning.

Thermal Performance

Chip junction temperatures typically stay between 55–70°C with properly conditioned coolant — dramatically cooler than the 80–95°C range common on air-cooled units running at maximum. Cooler chips mean longer lifespans, fewer thermal cycling failures, and more consistent hash delivery over years of operation.

Infrastructure Requirements

The S21 XP Hyd is not a plug-and-play device. It demands purpose-built infrastructure. Here is a realistic breakdown of what you need.

Electrical

• Power input: 3-phase 380–415V AC (industrial power). This is NOT a 240V/single-phase machine
• Per-unit current draw: Approximately 8.6A per phase at 380V
• Circuit protection: Dedicated breakers with appropriate amperage rating per unit
• PDU requirements: Industrial-grade power distribution with per-outlet monitoring recommended
• Total system power (with CDU): Budget 6,000–6,500W per unit

Plumbing

• Quick-connect fittings: Compatible with Bitmain’s Hyd series connectors
• Manifold system: For multi-unit deployments, a supply/return manifold with ball valves for each unit allows individual isolation
• Pressure testing: Leak-test your entire loop at 1.5x operating pressure before powering on any units
• Drain points: Install low-point drains for maintenance and winterization

Cooling Infrastructure

• Dry cooler / radiator: Sized for total thermal load plus 20% headroom
• Pump: High-flow industrial pump capable of 8–10 L/min per unit at required pressure head
• Reservoir: Sufficient coolant volume to maintain stable temperatures during transient loads
• Temperature monitoring: Inlet and outlet temperature sensors with alerting

Environment

• Space: The unit itself is compact (410 × 170 × 209 mm), but you need space for the CDU, plumbing runs, and electrical distribution
• Ventilation: Minimal compared to air-cooled — the heat goes into the coolant, not the room air
• Leak detection: Water leak sensors under every unit and along plumbing runs. Non-negotiable

Noise Comparison: The Hydro Advantage

This is where the S21 XP Hyd earns its keep for operators who care about their environment and their hearing.

The difference between 50 dB and 76 dB is not incremental — it is perceived as roughly 6x louder to the human ear (every 10 dB represents a doubling of perceived loudness). The S21 XP Hyd can operate in an adjacent room without hearing protection. The air-cooled S21 XP absolutely cannot.

Note that 50 dB is the miner unit itself. Your CDU pumps and dry cooler fans will add noise to the overall system, typically 40–60 dB depending on the equipment. Still dramatically quieter than a room full of screaming air-cooled ASICs. For more on managing mining noise, check our ASIC Noise Reduction Guide.

Profitability Analysis: Running the Numbers

Profitability is the only metric that matters for most operators. Here is a transparent breakdown at various electricity rates using February 2026 network conditions (difficulty ~110T, BTC price ~$96,000, block reward 3.125 BTC).

Critical notes on these numbers:

• Revenue figures are based on current network difficulty and BTC price. Both fluctuate significantly
• Power costs above do not include CDU/cooling infrastructure power. Add 5–15% to the power cost column for realistic total system economics
• Hardware acquisition cost (typically $6,000–$10,000 depending on market conditions) is not factored into daily profit — ROI at $0.07/kWh is approximately 2.5–3 years
• Canadian miners with hydroelectric rates in the $0.04–$0.06/kWh range are in the sweet spot for this machine

The breakeven electricity rate (where revenue equals power cost alone) sits around $0.125/kWh. Factor in CDU power and infrastructure amortization, and the real breakeven is closer to $0.11/kWh. If your all-in electricity rate is above that, this machine does not make economic sense unless you are capturing and monetizing the waste heat. For a full profitability deep dive, see our Is Bitcoin Mining Profitable in 2026? analysis.

Comparison: S21 XP Hyd vs. S21 XP vs. S21 Pro vs. Whatsminer M63S

Context matters. Here is how the S21 XP Hyd stacks up against the alternatives that miners are actually choosing between.

S21 XP Hyd vs. S21 XP (Air-Cooled)

Same chip generation, radically different deployment. The Hyd variant delivers 75% more hashrate and 11% better efficiency than its air-cooled sibling. The tradeoff is infrastructure complexity: the air-cooled S21 XP runs on standard 220–277V single-phase power and needs nothing but electricity and internet. The Hyd requires a complete water cooling infrastructure.

For operators who already have or are building hydro infrastructure, the XP Hyd is the obvious choice: more hash per rack unit, better efficiency, dramatically less noise. For operators adding a few machines to an existing air-cooled facility, the air-cooled S21 XP at 13.5 J/TH is still excellent.

S21 XP Hyd vs. S21 Pro (Air-Cooled)

The S21 Pro is the workhorse of air-cooled Antminers right now at 234 TH/s and 15 J/TH. The XP Hyd doubles the hashrate and improves efficiency by 20%. But the Pro costs significantly less per unit and requires zero plumbing. For home miners and small operators, the S21 Pro remains the practical choice. For facilities scaling beyond 5–10 PH/s, the XP Hyd’s density and efficiency advantages compound into meaningful operational savings.

S21 XP Hyd vs. Whatsminer M63S (Hydro)

This is the head-to-head that matters for hydro operators. The S21 XP Hyd dominates on efficiency: 12 J/TH vs. 18.5 J/TH. That is a 35% efficiency advantage — meaning the M63S burns 35% more electricity per terahash. The S21 XP Hyd also delivers more hashrate (473 vs. ~410 TH/s) while consuming less power (5,676W vs. 7,215W). The M63S weighs almost twice as much and comes with only a 180-day warranty versus Bitmain’s 365-day coverage.

The only scenario favoring the M63S is price: if you can acquire M63S units at a deep discount, the lower acquisition cost might offset the efficiency gap. But on a $/TH/day basis, the S21 XP Hyd wins convincingly.

For a broader comparison of top mining hardware, see our Best Bitcoin Miners 2026 guide.

Heat Recovery: The Space Heater Potential

Here is where the S21 XP Hyd becomes genuinely exciting for the Mining Hacker community: water-cooled heat recovery is the premium tier of dual-purpose mining.

Air-cooled miners dump heat into room air, which is fine for space heating but difficult to direct precisely. The S21 XP Hyd puts all 5,676W of thermal energy directly into a water loop. That heated water can be routed through:

• Radiant floor heating: Hot water from the miner’s return loop feeds directly into hydronic floor heating systems
• Domestic hot water preheat: A heat exchanger transfers mining heat to your domestic hot water tank, reducing water heating costs
• Greenhouse heating: Closed-loop water heating for year-round growing in cold climates
• Pool/hot tub heating: Direct or heat-exchanged transfer to recreational water features
• Workshop/garage heating: Hydronic fan coils convert the heated water back to warm air in specific zones

At 5,676W of continuous thermal output, a single S21 XP Hyd produces approximately 19,370 BTU/hour — equivalent to a decent-sized portable space heater running at maximum. In a Canadian winter, this meaningfully offsets heating costs while simultaneously mining Bitcoin. The economics shift dramatically: that $7–$12/day in mining profit plus $5–$10/day in displaced heating costs means the machine is effectively generating $12–$22/day of total value.

This is exactly the dual-purpose mining philosophy we champion at D-Central. To explore this further, check out our Bitcoin Space Heaters page and the Bitcoin Mining Heat Recovery: 25+ Real-World Applications guide.

Who Should Buy the S21 XP Hyd?

Ideal Buyers

• Small-to-mid mining facilities (1–50 PH/s) building out purpose-built infrastructure with hydro cooling from the start
• Operators upgrading from older hydro units (S19 Hyd, S19 XP Hyd) who already have water cooling infrastructure in place
• Canadian miners with access to cheap hydroelectric power ($0.04–$0.07/kWh) and cold ambient temperatures for efficient heat rejection
• Heat recovery enthusiasts building integrated mining/heating systems where the water loop serves double duty
• Noise-sensitive deployments where air-cooled ASICs are not an option due to noise restrictions

Not Ideal For

• Home miners without existing hydro infrastructure — the cost of building a water cooling loop from scratch for 1–2 units rarely makes economic sense. Look at the Antminer S21 (air-cooled) instead
• Operators paying above $0.11/kWh — the math does not work without heat recovery value
• First-time miners — if you are just starting out, build operational knowledge with air-cooled units first. See our How to Start Bitcoin Mining guide
• Facilities with only single-phase 240V power — the S21 XP Hyd requires 3-phase industrial power

Maintenance and Long-Term Reliability

Routine Maintenance

• Coolant quality checks: Test pH, conductivity, and particulate levels monthly
• Coolant replacement: Every 6–12 months depending on chemistry and filtration quality
• Filter replacement: Inline filters should be changed when pressure differential exceeds spec
• Leak inspection: Visual inspection of fittings and connections weekly
• Firmware updates: Keep firmware current for hashrate optimization and security patches

Common Failure Modes

• Coolant contamination: The #1 cause of hydro unit failures. Poor water quality corrodes water blocks and clogs micro-channels
• Fitting leaks: Quick-connect fittings can develop leaks from repeated connection/disconnection or thermal cycling
• Hashboard failure: Same as air-cooled units — individual ASIC chip failures can take down a hashboard
• Control board issues: Rare but possible, same as any Antminer generation

When repairs are needed, D-Central’s ASIC Repair service handles hydro units with full component-level diagnostic capability. We have been repairing Antminers since the S9 era and have specific tooling and expertise for the hydro series. Our S21 XP repair page details the specific services available for this model.

Should You Wait for the S21 XP+ Hyd?

Bitmain has announced the S21 XP+ Hyd, shipping mid-2025, with 500 TH/s at 11 J/TH. That is a 5.7% hashrate bump and 8.3% efficiency improvement over the standard XP Hyd. Worth waiting for?

If you are still in the infrastructure planning phase, waiting for the XP+ Hyd makes sense. If your facility is built and ready, every day without hashing is lost revenue. At current network difficulty and BTC price, the S21 XP Hyd generates positive ROI from day one (at competitive electricity rates). Mining is a time-sensitive business — the difficulty adjustment waits for no one.

The XP+ also typically commands a premium at launch. The original XP Hyd may see price reductions as the newer model ships, creating a potential buying opportunity for budget-conscious operators.

Verdict: The S21 XP Hyd Earns Its Place

The Antminer S21 XP Hyd is not for everyone, and it does not pretend to be. It is a specialized, high-performance machine that demands purpose-built infrastructure and operational competence. But for the operators who meet those requirements, it delivers:

• Industry-leading efficiency at 12 J/TH among hydro-cooled miners
• Massive hashrate density — 473 TH/s in a compact, lightweight package
• Operational quiet at ~50 dB, enabling deployments impossible with air-cooled units
• Premium heat recovery potential via the integrated water loop
• Bitmain’s 365-day warranty and the backing of the largest ASIC manufacturer in the world

For Canadian miners with hydroelectric power and cold winters, this machine is almost purpose-built for your conditions: cheap electricity, efficient heat rejection through cold ambient, and a water loop that can double as home heating infrastructure. That is the Mining Hacker playbook in action — taking institutional-grade hardware and making it work for your sovereign operation.

At D-Central Technologies, we stock, deploy, and repair the full Antminer lineup including the S21 XP Hyd. Whether you are planning your first hydro-cooled build or scaling an existing operation, contact our team for hardware sourcing, deployment consulting, and ongoing repair support.

Frequently Asked Questions