Bitmain's Antminer S21+: Full Hardware Overview

The S21+ arrives at the start of a hashprice recovery window (~$60/PH/day) and gives operators a fresh mid-tier choice in Bitmain's now-mature S21 generation. This overview covers full specs, current economics, and where the S21+ sits relative to its siblings.

TLDR

• Mid-tier air-cooled S21 at 216 TH/s and 16.5 J/TH. A 6% efficiency improvement over the base S21 (17.5 J/TH), priced below the S21 Pro (15.0 J/TH).
• Breakeven electricity cost: ~$0.152/kWh at ~$60/PH/day hashprice (late January 2025). Comfortable buffer for industrial operators.
• Value proposition is acquisition cost, not operating cost. The S21+ draws more power than the S21 Pro (3,564W vs. 3,510W) despite producing less hashrate — buyers should expect meaningfully lower per-unit pricing.
• Forward curve context: Luxor's Hashrate Forward Market is pricing in ~$55.25/PH/day over the next six months, compressing daily profit by ~$1/machine vs. spot.
• LuxOS autotuning closes part of the gap to the S21 Pro and XP, extending the S21+'s effective service life as fleet efficiency standards rise.

Background

Bitmain has steadily expanded the S21 generation since the original S21 launched in late 2023. The T21 (October 2023) anchored the mid-tier with 190 TH/s at 19.0 J/TH, the S21 base (December 2023) shipped at 200 TH/s and 17.5 J/TH, the S21 Pro (March 2024) introduced 15.0 J/TH efficiency at 234 TH/s, and the S21 XP (mid-2024) pushed the air-cooled flagship to 270 TH/s at 13.5 J/TH. The S21+, released January 31, 2025, slots into the lineup as a 216 TH/s upgrade from the base S21, with a 6% efficiency improvement (16.5 vs 17.5 J/TH).

The S21+ is a modest upgrade in absolute terms — 16 TH/s and 1.0 J/TH better than the base S21 — but a meaningful one strategically. It gives buyers an air-cooled S21 option that's newer than the 2023-launched base, more affordable than the S21 Pro, and shipping immediately rather than competing for secondary market supply. For operators expanding fleet capacity in early 2025, the S21+ is the freshest mid-tier air-cooled choice.

Antminer S21+ Specifications

Where the S21+ Sits in the S21 Air-Cooled Lineup

The S21 generation air-cooled stack as of the S21+ launch:

The S21+ at 16.5 J/TH is a step up from the base S21 (17.5 J/TH) and T21 (19.0 J/TH), but a step down from the S21 Pro (15.0 J/TH) and S21 XP (13.5 J/TH). It's a calibration play: buyers who want better-than-base efficiency without paying Pro pricing have a clear choice now. Hashrate-wise, the S21+'s 216 TH/s threads the same needle — 16 TH/s ahead of the base, 18 TH/s behind the Pro.

One thing worth flagging: at 3,564W, the S21+ draws more power than the S21 Pro (3,510W) despite producing less hashrate. The Pro is denser and more efficient in every dimension. The S21+'s value proposition is therefore acquisition cost, not operating cost — buyers should expect the S21+ to price meaningfully below the Pro on a per-unit basis.

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+ daily profitability across electricity costs at that hashprice.

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+ nameplate specs: 216 TH/s, 3,564 W (85.536 kWh/day). Breakeven electricity cost approximately $0.152/kWh.

The S21+ clears positive margin from $0.04 through $0.12/kWh. Breakeven electricity cost lands at approximately $0.152/kWh — a comfortable buffer for industrial operators. At $0.06/kWh, daily profit clears $7.80 per machine; at $0.04/kWh it pushes past $9.50. Buyers in the $0.13–$0.15/kWh range should think carefully about post-purchase hashprice scenarios, since the unit has tighter margins than the more efficient S21 Pro and XP.

Forward context: Luxor's Hashrate Forward Market is currently pricing in an average hashprice of $55.25/PH/day over the next six months. That implies modest spot compression. Buyers modeling S21+ economics over a multi-month window should anchor to the forward curve, which would compress daily profit figures by roughly $1 per machine across the table.

Fleet Efficiency Context

At 16.5 J/TH, the S21+ sits comfortably in the sub-19 J/TH top revenue-per-watt tier on Luxor's Energy Hashprice Index — but not by much. The 19 J/TH boundary that separates the top tier from the next tier sits just 2.5 J/TH above the S21+'s nameplate. That's a thinner buffer than the S21 Pro (4 J/TH below) or S21 XP (5.5 J/TH below).

Translation: as global fleet efficiency continues to improve, the S21+ will move toward the boundary of the top tier faster than its more efficient siblings. For operators thinking about a 3–5 year deployment window, that's worth modeling. For a 1–2 year acquisition-cost-driven decision, it matters less.

LuxOS Firmware Compatibility

LuxOS supports the S21 series including the S21+. For S21+ operators, the efficiency gains from LuxOS autotuning are particularly relevant: closing some of the J/TH gap to the S21 Pro and XP variants through firmware-level tuning is the easiest path to extending the unit's effective service life as fleet efficiency standards rise.

Explore LuxOS at luxor.tech/firmware.

Who Should Buy the S21+?

• Operators expanding air-cooled fleet capacity at the lowest possible per-unit cost in the S21 generation's current-gen tier (excluding base/T21).
• Buyers running existing fleets of older Antminers (S19j Pro, S19 XP) looking to refresh into the S21 generation without paying S21 Pro pricing.
• Operators with sub-$0.08/kWh power who want a fresh mid-tier S21 option and can absorb the slight efficiency disadvantage versus the Pro variant.
• Buyers running LuxOS who can autotune the S21+ to recover additional efficiency and partially close the gap to the more expensive S21 Pro.

Where to Buy

For S21+ 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.