At 288 TH/s and 17.0 J/TH, it sits below the S21 Hydro, S21+ Hydro, and S21 XP Hydro on both hashrate and efficiency, but ships at a lower acquisition cost per unit. This overview covers full specs, April 2025 economics, and how the S21e Hydro fits for operators looking to expand hydro capacity at the lowest possible upfront cost.

Background

Bitmain rolled out the S21 hydro lineup across a 15-month window. The S21 XP Hydro arrived first in June 2024 as the efficiency flagship at 12.0 J/TH. The S21 Hydro at 335 TH/s and S21+ Hydro at 358 TH/s followed in January and February 2025, filling out the high-performance middle tier. The S21e Hydro, released April 1, 2025, completes the family as the entry-level hydro option.

Unlike the rest of the S21 hydro stack, the S21e Hydro is not designed to compete on raw efficiency. At 17.0 J/TH, it actually sits below the air-cooled S21+ (16.5 J/TH) on the J/TH curve. What it offers instead is hydro cooling at the lowest acquisition cost in the S21 hydro line — a meaningful proposition for operators with hydro infrastructure already in place who want to expand fleet hashrate without paying premium pricing for the XP or + variants.

Antminer S21e Hydro Specifications

Where the S21e Hydro Sits in the S21 Hydro Lineup

The S21 generation now has four hydro-cooled variants. Positioning at a glance:

The pattern is clear: the S21e Hydro is the most affordable per-unit hydro option in the lineup but the least efficient. For an operator deciding between variants, the choice comes down to power cost. At sub-$0.05/kWh, the efficiency gap between the S21e and the higher-tier models matters less in absolute dollar terms, and the lower acquisition cost wins. At higher electricity costs, the efficiency advantage of the S21+ Hydro or S21 XP Hydro starts to outweigh the upfront savings.

Hashcost Breakeven Analysis

USD hashprice on April 1, 2025 was $46.93 per PH/day (Luxor Hashprice Index). The table below shows S21e Hydro daily profitability across a range of electricity costs at that hashprice.

At 17.0 J/TH, the S21e Hydro has tighter margins than the higher-efficiency hydro models. Breakeven electricity cost lands at approximately $0.115/kWh — meaningfully lower than the S21 XP Hydro’s ~$0.16/kWh breakeven at the same hashprice. Operators above $0.10/kWh power should think carefully before choosing the S21e over a more efficient variant.

It’s worth flagging that hashprice declined further during April 2025, hitting a low of $40.71 on April 7 before recovering. The economics in the table above are based on the higher entry-month hashprice; at the April average of $45.46/PH/day, profit figures compress by roughly $0.40–$0.50 per day across all electricity tiers.

Fleet Efficiency Context

Per Luxor’s April 2025 Hashrate Lookback: fleets running sub-19 J/TH were earning over $110 per MWh in mining revenues, while 19–25 J/TH and 25–38 J/TH tiers earned $90 and $60 per MWh respectively. At 17.0 J/TH, the S21e Hydro qualifies for the top revenue-per-watt tier — but only just. It sits closer to the 19 J/TH threshold than most of the S21 generation, leaving less margin if global fleet efficiency continues to improve.

LuxOS Firmware Compatibility

LuxOS — Luxor’s proprietary firmware for Bitmain Antminers — supports the S21 series including the S21e Hydro. For an entry-tier model like the S21e, firmware-level efficiency gains matter more than they do for the flagship variants: LuxOS autotuning can meaningfully close the gap between the S21e and higher-tier S21 hydro models. Operators looking to push the S21e Hydro’s effective J/TH lower will find LuxOS the most direct lever available.

Explore LuxOS at luxor.tech/firmware.

Who Should Buy the S21e Hydro?

• Operators with existing hydro cooling infrastructure who want to expand fleet hashrate at the lowest per-unit cost in the S21 hydro line.
• Miners with very low electricity costs (sub-$0.05/kWh) where the J/TH gap to the S21 XP Hydro matters less in absolute dollars than the upfront capital savings.
• Buyers prioritizing payback period over long-run efficiency, willing to accept tighter margins if hashprice compresses further.
• Operators running LuxOS who can use autotuning to recover some of the efficiency gap to higher-tier S21 hydro models.

Where to Buy

For S21e 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.

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.