Skip to main content
Crypto Miners Direct

Hardware guide

Antminer S21 XP - Specs, Power, Cooling and Who It Suits

Read Bitmain's published figures for the air-cooled S21 XP and the S21 XP Hyd., size their power and cooling, and know what to check before buying.

Last reviewed October 7, 2026 by James Emerson

The Antminer S21 XP is Bitmain's SHA-256 Bitcoin miner of the S21 generation. Bitmain publishes the air-cooled S21 XP at 270 TH/s and 3,645 W, or 13.5 J/TH (joules per terahash, i.e. watts ÷ TH/s), and the hydro-cooled S21 XP Hyd. at 473 TH/s and 5,676 W (12.0 J/TH). The air unit runs on single-phase 220–277 V; the hydro unit needs 380–415 V three-phase power and a liquid cooling loop. Every model figure below is manufacturer-published.

Key points

  • The air unit needs a dedicated 220–277 V circuit installed by a qualified electrician to local code; 120 V and 208 V are outside its range.
  • The Hyd. is not standalone: it needs coolant at 20–50 °C and 8–10 L/min.
  • Electricity cost per day = kW × 24 × price per kWh: $5.25 for the air unit at an illustrative $0.06 per kWh.
  • Before buying, confirm the hashrate version, the fitted power supply and the firmware.

Published specifications

S21 XP (air) S21 XP Hyd. (hydro)
Hashrate (typical, ±3%) 270 TH/s 473 TH/s
Power at the wall (typical, ±5%) 3,645 W 5,676 W
Efficiency (typical, ±5%) 13.5 J/TH 12.0 J/TH
Rated at 25 °C inlet air 35 °C inlet coolant
AC input 220–277 V single-phase, 50–60 Hz, 20 A 380–415 V three-phase, 50–60 Hz, 12 A max
Power supply APW171215, part of the machine APW11, part of the machine
Cooling Fans, 550 CFM (cubic feet per minute) maximum airflow Cold plates; coolant 20–50 °C, 8–10 L/min, ≤ 3.5 bar
Size (L × W × H) 450 × 219 × 293 mm 339 × 173 × 207 mm
Net / gross weight 18.7 / 21.5 kg 13.8 / 15.7 kg
Noise 76 dB(A), fans at maximum speed Not published
Operating conditions −20 to 45 °C air, 10–90% RH non-condensing, up to 2,000 m Ambient temperature and altitude not published; 10–90% RH non-condensing

Bitmain lists one hashrate version of each. Its support article gives 449 mm for the air unit's length; the table follows the current shop listing. Above 900 m the air unit's maximum operating temperature falls 1 °C per 300 m, to about 41.3 °C at 2,000 m.

Plan on the tolerance: the upper power figures are 3,645 × 1.05 = 3,827 W and 5,676 × 1.05 = 5,960 W.

What the efficiency means for running cost

energy per day (kWh)      = power (kW) × 24
electricity cost per day  = power (kW) × 24 × price per kWh
kWh per TH/s per day      = J/TH × 0.024

The prices per kWh are illustrative inputs.

Machine Power Energy per day At $0.04/kWh At $0.06/kWh At $0.08/kWh
S21 XP 3.645 kW 87.48 kWh $3.50 $5.25 $7.00
S21 XP Hyd. 5.676 kW 136.22 kWh $5.45 $8.17 $10.90

That is 13.5 × 0.024 = 0.324 kWh per TH/s per day for the air unit and 0.288 kWh for the Hyd. (before pumps and dry cooler), or $0.0194 and $0.0173 at $0.06.

Revenue depends on network difficulty, block reward and price; use the mining calculator for current values. Nothing here predicts earnings.

Compared with earlier Bitmain generations

Published typical values; the last column, 270 × J/TH, is the power each model needs for 270 TH/s.

Air-cooled model Hashrate Power Efficiency Power for 270 TH/s
S19 Pro (110T version) 110 TH/s 3,250 W 29.5 J/TH 7,965 W
S19 XP (141T version) 141 TH/s 3,031.5 W 21.5 J/TH 5,805 W
S21 200 TH/s 3,500 W 17.5 J/TH 4,725 W
S21 XP 270 TH/s 3,645 W 13.5 J/TH 3,645 W
S23 305 TH/s 3,355 W 11.0 J/TH 2,970 W

The S21 XP uses 23% less energy per terahash than the S21, 37% less than the S19 XP and 54% less than the S19 Pro. At an illustrative $0.06 per kWh, the 2,160 W gap to S19 XP efficiency at 270 TH/s is 51.84 kWh, or $3.11, a day. The S23 is listed lower still; the site's miner rankings sort published models by lowest J/TH, among other criteria.

Among hydro models, Bitmain publishes 257 TH/s at 5,346 W (20.8 J/TH) for the S19 XP Hyd., 335 TH/s at 5,360 W (16.0 J/TH) for the 335T S21 Hyd., and 580 TH/s at 5,510 W (9.5 J/TH) for the S23 Hyd. The S21 XP Hyd. uses 42% less energy per terahash than the S19 XP Hyd. and 25% less than the S21 Hyd. Compare air with air and hydro with hydro, since the rating conditions differ.

Electrical requirements

S21 XP. Current = watts ÷ volts (power factor ≈ 1): 16.57 A at 220 V, 15.19 A at 240 V and 13.16 A at 277 V, or 17.40, 15.95 and 13.82 A at 3,827 W. Bitmain publishes a 20 A input current. Under North American practice (NEC) a continuous load is commonly limited to 80% of the breaker rating, so sizing on 20 A gives at least 20 ÷ 0.8 = 25 A of breaker capacity; other regions follow their own codes. Bitmain's support specification also lists an "adapted AC output power requirement" of 4,000 W; give both figures to your electrician.

In the US, 240 V split-phase is in range and 277 V (phase to neutral on a 480Y/277 V service) is the top of it; 120 V and 208 V are not. Bitmain warns that the wrong voltage can damage the machine, and its manual requires an earthed outlet near the equipment and easy to reach. See 220V Bitcoin Mining.

S21 XP Hyd. Three-phase current = W ÷ (√3 × V × PF): 8.62 A per line at 380 V and 7.90 A at 415 V, against Bitmain's 12 A maximum (12 ÷ 0.8 = 15 A under the 80% practice). The usual US three-phase voltages, 208 V and 480 V, are both outside 380–415 V, so a US site needs a transformer or a supply built for that range. Bitmain's manual also requires an external surge protective device complying with IEC/EN 61643-11 and a disconnecting device that opens L1, L2 and L3 together. See Three-Phase Mining Equipment.

A qualified electrician must design and install all of this to local code. Never bypass or oversize protection.

Cooling and noise

Air. All the power becomes heat: 3.645 kW × 3,412 ≈ 12,437 BTU/h per machine. From heat (BTU/h) = 1.08 × CFM × temperature rise, Bitmain's 550 CFM maximum airflow implies about 12,437 ÷ (1.08 × 550) ≈ 21 °F (11.6 °C) from intake to exhaust, and Bitmain notes airflow falls when the machine is dusty or poorly ventilated. The 76 dB(A) is stated at 30 °C with fans at maximum speed and no distance; two machines add about 3 dB. Bitcoin Mining at Home covers enclosures and ducting.

Hydro. The Hyd. has no fans; the noise comes from pumps and dry-cooler fans, usually outdoors. Each unit puts about 5.676 × 3,412 ≈ 19,367 BTU/h into the coolant. For plain water, temperature rise ≈ 5,676 ÷ (flow in kg/s × 4,180): about 10 °C at 8 L/min (0.133 kg/s) and 8 °C at 10 L/min.

The loop must meet Bitmain's figures: 20–50 °C inlet, 8–10 L/min per unit, at most 3.5 bar, antifreeze, pure water or deionized water within stated pH ranges, and an OD10 connector (the support article says DN10, so check the unit). The miner cannot start below 20 °C inlet, and its firmware stops it above 50 °C. Bitmain's manual pairs it with its ANTSPACE HK3 hydro container; the shop listing cites the ANTSPACE HW7 manual for coolant care. See Air vs Hydro Bitcoin Miners.

Who each version suits

The S21 XP suits one to a few dozen machines on 220–277 V single-phase circuits, in a space that tolerates the noise and keeps intake air within −20 to 45 °C.

The S21 XP Hyd. suits sites with, or building, a hydro loop and 380–415 V three-phase power: hot or dusty locations, noise-limited sites, dense builds and projects that can use warm water.

The site's Antminer S21 XP and Antminer S21 XP Hyd. listings show these specifications with their source.

Before you buy

  1. Model and version. Bitmain publishes 270 TH/s for the S21 XP and 473 TH/s for the Hyd.; the S21 XP+ Hyd. and S21 XP Imm. are separate models. If a listing states another hashrate, ask the seller for its source and matching power figure.
  2. Power supply and input. Bitmain's manuals name the APW171215 (air) and APW11 (Hyd.) as part of the machine. Confirm it is fitted, which power cord comes with it, and that the input suits your site.
  3. Firmware. The web interface shows the version as a date; ask what is installed. Bitmain warns that power loss during an upgrade means returning the unit for repair, and that it is not liable for damage if function settings are changed without its consent.
  4. Warranty and condition. Get in writing who provides warranty cover, and for how long. For a used unit, see How to Inspect and Test a Used ASIC Miner.

Sources