How to choose an ASIC miner: a step-by-step guide

Choose an ASIC miner based on the electricity price you will actually pay and on the machine's efficiency (J/TH) – not on the highest hashrate. First pick a coin and algorithm, then work out the electricity price up to which the machine pays off, and only then decide whether it will run at home or in hosting, and whether to buy new or used.

Summary

• An ASIC can only run one algorithm. By choosing a machine, you also choose the coins it can mine.
• The key figure is the break-even electricity price: earnings per unit of hashrate ÷ (efficiency × 0.024). Below it the machine makes money, above it it loses money.
• A large ASIC runs at 75 dB and draws 3–4 kW. At home it only pays off with cheap or self-generated electricity; otherwise hosting is the better option.
• A used machine is cheaper but has worse efficiency and a shorter remaining lifespan. Check the hash boards and the warranty.
• Always calculate payback after deducting electricity, with a margin for rising difficulty.

Step 1: Choose a coin and algorithm

An ASIC miner is a single-purpose machine. A Bitcoin Antminer S21 cannot mine Kaspa, and a Litecoin machine cannot mine Bitcoin. Choosing a machine therefore means choosing an algorithm:

• SHA-256 – Bitcoin and Bitcoin Cash. The greatest liquidity, but the toughest competition.
• Scrypt – Litecoin and Dogecoin at the same time (merged mining).
• Equihash – Zcash.
• kHeavyHash – Kaspa.
• Blake2b-Sia – BTCB2 and Siacoin.

One algorithm usually supports several coins, so if earnings from one drop you can switch to another. Also bear in mind that a coin may change its algorithm or rules – the ASIC then becomes useless for that network.

Step 2: Find out your real electricity price

Electricity is the biggest operating cost of ASIC miners. The price per kWh includes the energy itself, distribution, taxes and fees. The easiest way is to take the total amount from your annual bill and divide it by the number of kWh consumed.

You calculate a machine's daily consumption as its power draw in kW × 24. An Antminer S21 Pro+ drawing 3,675 W uses 88.2 kWh a day, over 2,600 kWh a month. A household using 600–700 kWh a month (an example from our earlier calculation) would roughly quadruple its consumption. Even a difference of one koruna per kWh then amounts to over CZK 2,600 a month.

Step 3: Work out the electricity price up to which the machine pays off

This is the most important step. Break-even electricity price = daily earnings per unit of hashrate ÷ (efficiency × 0.024). For Bitcoin, 1 TH/s currently earns 0,84 Kč a day, so the break-even comes out at roughly 35 ÷ J/TH.

The values apply at today's difficulty and exchange rate, as of 18 Oct 2026. The same calculation works for every coin: for Zcash, 1 kSol/s currently earns 0,93 Kč, so an Antminer Z15 Pro at 3.3 J/kSol pays off up to roughly CZK 11.7/kWh. We explain exactly what J/TH means in our article on ASIC power consumption and efficiency.

Leave yourself a margin. Network difficulty rises over the long term, and for Bitcoin the block reward is halved once every four years. A machine that only just pays off above your electricity price may be loss-making within a few months.

Step 4: Decide between home and hosting

Take the Antminer S21 Pro+ 245 TH/s. At today's difficulty and exchange rate it mines 245 × CZK 0.84 ≈ CZK 206 gross per day (as of 18 Oct 2026).

Besides price, operation matters too. A large air-cooled ASIC runs at around 75 dB, as loud as a vacuum cleaner, and a 3.5 kW power draw needs a dedicated circuit for a continuous load of around 16 A (leave the design to an electrician). At home it mainly makes sense with your own electricity from surplus solar power or with a quiet machine built for the home.

In hosting, the data centre takes care of power, cooling and monitoring. Locations differ in price and uptime: the cheapest, Nigeria #2, has 97.12% uptime, while Norway – Arctic at USD 0.064/kWh has 99.85%. An overview is on our ASIC miner hosting page.

Step 5: New or used?

A used machine costs less but is usually a generation older, so it has a worse J/TH and becomes loss-making sooner. Its fans, power supply and hash boards also have a shorter remaining lifespan. With a second-hand unit, always find out:

1. whether all hash boards are running and what the actual hashrate is compared with the nominal one,
2. chip temperatures at full load,
3. which firmware it has and whether it has been overclocked,
4. whether it has a warranty and who provides it.

A detailed comparison is in our article new or used ASIC. You will also find used machines with a warranty in our second-hand section.

Step 6: Calculate payback

Payback in days = machine price ÷ daily profit after deducting electricity. A calculation “excluding electricity”, which used to appear in rankings, is misleading – for large machines, electricity makes up most of the costs.

Also include shipping, customs duty and VAT, any hosting, and a margin for falling earnings. Our mining investment calculator works out exact figures for a specific machine and your electricity price.

Step 7: Check the manufacturer, warranty and service

• Manufacturer: prefer established brands (Bitmain, MicroBT, Canaan, IceRiver, Goldshell). With new brands, check that the machine really exists and is being delivered.
• Warranty: find out how long it lasts and where it is handled. If the warranty is handled by the manufacturer abroad, expect the machine to be out of operation for a long time.
• Service: fans and power supplies fail most often. A service centre in the Czech Republic is an advantage – PC Praha repairs ASIC miners right in Prague.
• Space and noise: dimensions, a weight of around 15 kg, and the need for air intake and exhaust.

Pre-purchase checklist

1. I know which coin and which algorithm I want to mine.
2. I know my electricity price including distribution.
3. The machine's break-even point is comfortably above my electricity price.
4. I have the location sorted: at home with a dedicated circuit and ventilation, or hosting.
5. I have calculated payback after deducting electricity.
6. I know who provides the warranty and where the service centre is.

What next

• ASIC miner profitability – a live table with earnings and payback for all machines in our range.
• Most profitable ASIC miners – which specific machines earn the most today across coins.

Sources

• Bitcoin Magazine: Antminer S21 Pro specifications
• Hashrate Index: Antminer S21+ specifications