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Antminer S21 Performance Review

Antminer S21 Performance Review

Feb 6, 2024

Antminer S21 Performance Review

The Antminer S21, Bitmain's latest iteration in the Antminer series, has been designed to be the most efficient and powerful Bitcoin mining rig to date. Since its announcement at Bitmain's 2023 digital mining summit and the commencement of shipping in January 2023, the mining community has eagerly awaited performance evaluations. This article is based on a video review produced by Luxor which included a rigorous performance test of the Antminer S21, building upon the initial review which covered the rig's design and specifications.

Testing Methodology

The performance test was conducted in a temperature-controlled environment, which allowed for the assessment of the Antminer S21's capabilities under various thermal conditions. The temperatures selected for the tests were 10°C, 25°C, and 40°C, with each level sustained for durations of 30 to 60 minutes to ensure accurate and consistent results. The primary metrics of interest were hash rate, power consumption, and efficiency.

Test Results at Varied Temperatures

At the outset of the tests, the Antminer S21 was placed in a 10°C setting. Results demonstrated a hash rate of 200 terahashes per second (TH/s) and a power consumption of 3470 watts, which equates to 17.4 joules per terrahash (J/TH), a figure marginally surpassing the advertised efficiency. It was noted that the power supply unit (PSU) increased its voltage output from the standard 13 volts to 14 volts during this low-temperature operation.

When the temperature was elevated to 25°C, the S21's performance slightly increased to 203 TH/s, although power usage rose to 3620 watts, resulting in an efficiency of 17.9 J/TH. Pushing the temperature further to 40°C, the rig maintained a hash rate of 202 TH/s but experienced increased power consumption at 4000 watts, leading to a reduced efficiency of 19.8 J/TH.

Temperature Regulation and Low Power Mode

The Antminer S21's firmware includes a temperature management feature that comes into play above 40°C, where the device began to underclock to prevent overheating. Post-underclocking, the hash rate dipped to 185 TH/s, with power usage at 3700 watts and an efficiency of 20 J/TH. This adaptive underclocking allows the S21 to operate at temperatures 5°C higher than previous models.

Another noteworthy addition is the low power mode, which the S21 can employ to enhance efficiency. Underclocking the S21 at 16°C and 20°C showed the rig operating at 157 TH/s while achieving efficiencies of 16.1 J/TH and 16.3 J/TH, respectively.

Performance Consistency and Acoustic Levels

Despite slight potential margins for error in power accuracy and GUI hash rate reporting, repeated tests under various environmental conditions yielded consistent findings, affirming the reliability of the S21. It should be mentioned that the S21 is particularly loud, with noise levels outside the temperature-controlled box measured at 80 to 83 decibels, attributable to its high-powered fans.


The Antminer S21 demonstrates robust performance across a spectrum of temperatures, meeting its advertised hash rate while providing opportunities for further efficiency gains through low power mode and hash rate optimization. Its design innovations support enhanced thermal management and future-proofing against the increasing mining difficulty anticipated for the 2024 Bitcoin halving event.

For those considering the purchase of an Antminer S21, the ASIC trading desk is available to assist in securing the best deal on these top-tier miners. Additionally, support for the S21 will be forthcoming from the firmware team, ensuring ongoing improvements and optimizations for users of this mining rig.


Current Block Height

Current Mempool Size

Current Difficulty