Full-size Bitcoin miners are built for supplies in the 200–240 V class, which people loosely call 220 V. If your country's standard outlet voltage is 220–240 V, you already have the right voltage and need a dedicated circuit with enough capacity. In North America you add a 240 V circuit of the kind used for a dryer, range or vehicle charger. In both cases the questions are the same: is the voltage inside the miner's published range, and how much continuous current can the circuit carry.
A qualified electrician must design and install the circuit to your local code. Use this guide to understand the numbers and to ask the right questions.
Key points
- A 3,500 W miner draws 14.58 A at 240 V and would need 29.17 A at 120 V. Higher voltage means lower current.
- 208 V is not the same as 240 V. Some miners publish a minimum input of 220 V, which 208 V does not meet.
- Under the North American 80% continuous-load rule, a 30 A 240 V circuit carries one 3,500 W miner and a 50 A circuit carries two.
- A circuit shared by several miners needs a PDU or sub-panel with protection sized for each miner's cord.
- A full-size air-cooled miner adds about 11,900 BTU/h of heat and industrial-level noise to a home.
Why miners want 200–240 V
Power is voltage multiplied by current, and a miner's power supply draws roughly constant power. Doubling the voltage halves the current. Lower current means smaller conductors, cooler connectors and less energy lost in the wiring.
The second reason is the power supply's input range. Bitmain publishes 220–277 V for the Antminer S21 and 200–240 V for the Antminer S19k Pro. MicroBT publishes 220–240 V for the WhatsMiner M60S+. These are manufacturer-published figures, and none of them includes 120 V. Always check the range for the exact model you intend to buy.
Three supplies that get called 220 V
| Supply | Where the voltage comes from | Where you find it |
|---|---|---|
| 240 V split-phase | Between the two hot legs of a 120/240 V service. Each leg is 120 V to neutral. | North American houses |
| 208 V line-to-line | Between two phases of a 208Y/120 V three-phase service | North American apartment blocks and commercial buildings |
| 220–240 V line-to-neutral | Between one phase and neutral of a 380–415 V three-phase network | Most countries outside North America |
To the miner these are all an AC voltage across its input. What differs is the actual voltage and how the circuit is protected.
A North American 240 V miner circuit uses two hot conductors and a ground on a two-pole breaker. The miner itself does not use the neutral. A 230 V circuit elsewhere uses one live conductor, a neutral and an earth.
The 208 V case needs care. Because the phases are 120° apart, two 120 V legs give 120 × √3 = 208 V, not 240 V. That has two consequences:
- Current is 240 ÷ 208 = 1.15 times higher for the same power. A 3,500 W machine draws 16.83 A instead of 14.58 A.
- 208 V is below the 220 V minimum that some manufacturers publish. Of the examples above, only the Antminer S19k Pro's published range of 200–240 V includes it.
If you are in a multi-unit or commercial building, have the voltage measured before you order a machine.
How many miners per circuit
The method, under North American practice:
- Continuous capacity = breaker rating × 0.8.
- Usable power = continuous capacity × voltage.
- Miner count = usable power ÷ miner power, rounded down. Use the miner's power with its published tolerance added.
Illustrative machine: 3,500 W, or 3,675 W with a 5% tolerance.
30 A, 240 V circuit. 30 × 0.8 = 24 A. 24 × 240 = 5,760 W. 5,760 ÷ 3,675 = 1.57, so one miner. Two would need 7,000 W, which is 29.17 A.
50 A, 240 V circuit. 50 × 0.8 = 40 A. 40 × 240 = 9,600 W. 9,600 ÷ 3,675 = 2.61, so two miners, drawing 7,350 ÷ 240 = 30.63 A at the top of their tolerance. Three would need 10,500 W, which is 43.75 A.
| Breaker | Continuous limit | Usable power at 240 V | Miners at 240 V | Usable power at 208 V | Miners at 208 V |
|---|---|---|---|---|---|
| 20 A | 16 A | 3,840 W | 1 | 3,328 W | 0 |
| 30 A | 24 A | 5,760 W | 1 | 4,992 W | 1 |
| 40 A | 32 A | 7,680 W | 2 | 6,656 W | 1 |
| 50 A | 40 A | 9,600 W | 2 | 8,320 W | 2 |
Two points follow from the table. A 20 A circuit that carries the machine at 240 V cannot carry it at 208 V. And adding breaker capacity does not always add a miner: 30 A carries no more full-size machines than 20 A at 240 V.
The table is based on calculated current. A manufacturer's published input current can be higher: Bitmain lists a 20 A AC input for the Antminer S21. Sized on 20 A per machine, each miner needs 20 ÷ 0.8 = 25 A of breaker capacity, and the 240 V counts become 0, 1, 1 and 2. The 30 A and 50 A results are the same on either basis. Your electrician decides which figure governs.
A circuit that feeds more than one miner cannot simply be split with a cable. Each miner's cord and inlet are rated for roughly 16 to 20 A, so they cannot be protected by a 40 A or 50 A breaker alone. The circuit should end at a PDU (power distribution unit) or small sub-panel with a breaker for each outlet. See PDUs.
Outside North America, circuits are sized under local rules rather than a flat 80%. The current calculation is the same: 3,500 W at 230 V is 15.22 A, and 15.98 A with tolerance.
Receptacles and plugs
The receptacle is chosen to match the circuit rating, not the miner. The main families:
- NEMA 6 series (North America): 250 V, two hots and ground, no neutral. The number after the dash is the amp rating, as in 6-20, 6-30 and 6-50.
- NEMA 14 series: 125/250 V with neutral and ground, used for dryers and ranges, as in 14-30 and 14-50.
- NEMA L6 locking series: twist-lock versions such as L6-20 and L6-30, common on PDU input cords.
- IEC 60309 industrial connectors: used in 230 V regions for dedicated circuits, commonly in 16 A and 32 A sizes.
- IEC 60320 C19/C20 and C13/C14: the appliance connectors on the miner end of the cord.
Household sockets in 230 V countries are often not enough. A UK plug is fused at 13 A, which is 2,990 W at 230 V. A 16 A socket supplies 3,680 W at 230 V, which leaves a 3,500 W machine with no margin once tolerance is added. A dedicated circuit with an industrial connector is the usual answer.
This guide does not prescribe a particular receptacle-to-miner cable, because the correct one depends on the circuit rating, the PDU and your code. Have the electrician fit a receptacle that matches the breaker, then choose a PDU or cord whose plug matches it, whose outlets match the miner's inlet, and whose rating covers the miner's current. Do not use travel adapters, unprotected splitters or light-duty extension cords.
Voltage drop
Wire has resistance, so some voltage is lost between the panel and the miner:
voltage drop = 2 × current × resistance per metre × one-way length
The factor of 2 accounts for the current travelling out and back. With illustrative values of 15 A, a 30 m run and a conductor resistance of 0.005 Ω per metre:
- Drop = 2 × 15 × 0.005 × 30 = 4.5 V, which is 1.9% of 240 V.
- Power lost in the cable = 4.5 V × 15 A = 67.5 W, around the clock. Over a year that is 0.0675 kW × 8,760 h = 591 kWh.
A thicker conductor has lower resistance and loses less. It matters most on long runs and on 208 V supplies that start near the bottom of the miner's range. Your electrician will size the conductor for both ampacity and voltage drop.
Heat and noise at home
Heat. Essentially all the power a miner draws becomes heat. 3.5 kW × 3,412 = 11,942 BTU/h, about the output of 2.3 portable 1,500 W heaters running without a break. A closed room will overheat quickly. The exhaust air needs a path outdoors and the intake needs a supply of cooler air within the machine's published operating temperature range.
Noise. Bitmain publishes a noise level of 76 dB(A) for the Antminer S21. A machine that loud is not practical in living space. Plan for a garage, basement or outbuilding with sound treatment, or look at low-noise home miners.
Energy and service capacity. One 3,500 W miner uses 84 kWh per day and 2,520 kWh per 30 days. It also occupies about 15 A of your 240 V service continuously. Ask the electrician to check that your panel and service have the capacity alongside your other large loads.
Before you order
- Identify your supply and have the voltage measured.
- Check the published input voltage range, power and input current for the exact model.
- Have a qualified electrician confirm service capacity and install a dedicated circuit.
- Choose a PDU or cord that matches the receptacle and the miner's inlet.
- Plan where the heat and noise will go.