Bitmain's Antminer S21+ Hydro: Full Hardware Overview
The Antminer S21+ Hydro is Bitmain's newest mid-tier hydro miner, launched February 1, 2025.
At 358 TH/s and 15.0 J/TH, it slots between the S21 Hydro and the flagship S21 XP Hydro on both hashrate and efficiency. Released just one month after the S21 Hydro refresh, the S21+ Hydro represents Bitmain's push to broaden hydro deployment beyond the high-end XP tier. This overview covers full specs, current hashprice economics, and where the S21+ Hydro fits in today's hydro lineup.
TLDR
- Mid-tier hydro at 358 TH/s and 15.0 J/TH. Slots between the S21 Hydro (16.0 J/TH) and S21 XP Hydro (12.0 J/TH) — a 6% efficiency gain over the S21 Hydro at a lower price than the XP.
- Breakeven electricity cost: ~$0.167/kWh at ~$60/PH/day hashprice (late January 2025). Strong margin buffer for industrial operators.
- Daily profit exceeds $13/machine at $0.06/kWh and pushes past $16/day at $0.04/kWh — the sweet spot for mid-density hydro deployments.
- Firmly in the sub-19 J/TH top revenue-per-watt tier with a 25% efficiency margin above the 20 J/TH boundary, protecting against declining hashprice environments.
- LuxOS autotuning can push below 15.0 J/TH, closing some of the gap to the S21 XP Hydro at lower cost.
Background
Hydro cooling has moved from a specialty deployment format to a mainstream option over the past 18 months. The S21 XP Hydro, released in June 2024, anchored the high-end of the segment at 12.0 J/TH. In January 2025, Bitmain refreshed the S21 Hydro to 335 TH/s and 16.0 J/TH. The S21+ Hydro, released February 1, 2025, completes the current S21 hydro stack and gives operators a true mid-tier option — better efficiency than the S21 Hydro, lower acquisition cost than the S21 XP Hydro.
The S21+ Hydro's 15.0 J/TH places it firmly in the top efficiency tier of currently-shipping ASICs. Combined with hydro's thermal advantages — quieter operation, smaller per-TH footprint, and tighter clock control — the S21+ Hydro is positioned for operators expanding capacity in immersion-ready or hydro-ready facilities who don't need the absolute peak efficiency of the XP variant.
Antminer S21+ Hydro Specifications
| Bitmain Antminer S21+ Hydro | |
|---|---|
| Hash Rate | 358 TH/s |
| Power Consumption | 5,370 W |
| Efficiency | 15.00 J/TH |
| Algorithm | SHA-256 |
| Cooling | Hydro (water-cooled) |
| Voltage | 380–415V (3-phase) |
| Operating Temperature | 5–45°C |
| Release Date | February 1, 2025 |
| Manufacturer | Bitmain |
| Live profitability & specs: hashrateindex.com/rigs/s21-plus-hyd |
Where the S21+ Hydro Sits in the S21 Hydro Lineup
The current S21 hydro lineup at launch:
| Model | Hash Rate | Power | Efficiency | Released |
|---|---|---|---|---|
| S21 XP Hydro | 473 TH/s | 5,676 W | 12.0 J/TH | Jun 2024 |
| S21+ Hydro | 358 TH/s | 5,370 W | 15.0 J/TH | Feb 2025 |
| S21 Hydro (335) | 335 TH/s | 5,360 W | 16.0 J/TH | Jan 2025 |
The S21+ Hydro is the natural mid-tier choice. Operators who need maximum efficiency and can pay the premium go to the S21 XP Hydro at 12.0 J/TH. Buyers prioritizing lowest acquisition cost per unit go to the S21 Hydro at 16.0 J/TH. The S21+ Hydro is for everyone in between: meaningful efficiency improvement over the S21 Hydro (15.0 vs 16.0 J/TH — a 6% gain) without paying XP pricing.
Hashrate positioning tells a similar story: 358 TH/s exceeds the S21 Hydro's 335 TH/s by ~7%, while the XP Hydro's 473 TH/s remains the lineup's density leader. For mid-density hydro deployments, the S21+ Hydro hits a balanced sweet spot.
Hashcost Breakeven Analysis
USD hashprice was trading at ~$60 per PH/day in late January and early February 2025 (Luxor Hashprice Index, $59.86 reading on February 3). The table below shows S21+ Hydro daily profitability across electricity costs at that hashprice.
| Electricity Cost | Revenue/Day | Power Cost/Day | Profit/Day | Status |
|---|---|---|---|---|
| $0.04/kWh | $21.48 | $5.16 | $16.32 | Profitable |
| $0.05/kWh | $21.48 | $6.44 | $15.04 | Profitable |
| $0.06/kWh | $21.48 | $7.73 | $13.75 | Profitable |
| $0.08/kWh | $21.48 | $10.31 | $11.17 | Profitable |
| $0.10/kWh | $21.48 | $12.89 | $8.59 | Profitable |
| $0.12/kWh | $21.48 | $15.47 | $6.01 | Profitable |
| $0.15/kWh | $21.48 | $19.33 | $2.15 | Marginal |
Based on ~$60/PH/day USD hashprice (Luxor Hashprice Index, late January / early February 2025; $59.86 reading on Feb 3, 2025). Calculated using S21+ Hydro nameplate specs: 358 TH/s, 5,370 W (128.88 kWh/day). Breakeven electricity cost approximately $0.167/kWh.
The S21+ Hydro generates positive margin across the full $0.04–$0.12/kWh range. Breakeven electricity cost lands at approximately $0.167/kWh — a comfortable buffer for North American and European industrial operators. At $0.06/kWh, daily profit clears $13/day per machine; at $0.04/kWh, it pushes past $16/day.
Forward hashrate context: Luxor's Hashrate Forward Market is currently pricing in an average hashprice of $55.25/PH/day over the next six months. That's a modest discount to spot — the market is pricing in some hashprice compression as network difficulty continues climbing, but not severe deterioration. Buyers modeling S21+ Hydro economics over a multi-month payback window should anchor to the forward curve rather than spot.
Fleet Efficiency Context
At 15.0 J/TH, the S21+ Hydro sits firmly in the sub-19 J/TH top revenue-per-watt tier on Luxor's Energy Hashprice Index. Operators running this efficiency class capture meaningfully higher revenue per megawatt than the 19–25 J/TH and 25–38 J/TH tiers — a structural advantage that compounds as global fleet efficiency continues to improve and network difficulty climbs.
For comparison: the S21+ Hydro's 15.0 J/TH is 25% more efficient than the 20 J/TH that defines the boundary between top and second tier, and roughly half the J/TH of the older S19 generation. That gap is what protects margin in a declining hashprice environment.
LuxOS Firmware Compatibility
LuxOS supports the S21 series including the S21+ Hydro. LuxOS unlocks autotuning, advanced power management, and real-time monitoring through the Luxor dashboard. For S21+ Hydro operators, the practical implication is that nameplate efficiency can be tuned: LuxOS can push the unit below 15.0 J/TH through autotuning, closing some of the gap to the S21 XP Hydro at lower cost.
Explore LuxOS at luxor.tech/firmware.
Who Should Buy the S21+ Hydro?
- Operators with hydro infrastructure who want a balance of efficiency and acquisition cost — the S21+ Hydro is meaningfully more efficient than the S21 Hydro but priced below the S21 XP Hydro.
- Industrial operators in the $0.04–$0.08/kWh range, where the S21+ Hydro's 15.0 J/TH efficiency generates strong margin without paying the XP premium.
- Miners expanding hydro deployment incrementally — the S21+ Hydro's mid-tier positioning makes it a flexible scaling unit when you don't need all-XP racks.
- Operators running LuxOS who can autotune the S21+ Hydro to recover additional efficiency — the firmware advantage stacks on top of the already-strong nameplate J/TH.
Where to Buy
For S21+ Hydro pricing, availability, and fleet-scale orders, reach out to Luxor's hardware trading desk via luxor.tech/hardware. Luxor's desk handles both single-unit and bulk institutional orders.
For live hashprice, real-time profitability calculations, and the latest ASIC market data, visit hashrateindex.com.
About Luxor Technology Corporation
Luxor delivers hardware, software, and financial services that power the global compute and energy industry. Its product suite spans Bitcoin Mining Pools, ASIC Firmware, Hardware trading, Hashrate Derivatives, Energy services, a Miner Management software, Commander, and a bitcoin mining data platform, Hashrate Index.
Disclaimer
This content is for informational purposes only, you should not construe any such information or other material as legal, investment, financial, or other advice.
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