Bitcoin mining is no longer profitable in the small.
Today, the mining landscape is dominated by two different mining strategies:
The Bitcoin mining process is a Proof of Work consensus mechanism.
What this means is miners need to prove they made an effort to find the suitable Bitcoin block. Mining pools reward users by the effort they put in (work), which they must prove by submitting their "shares" every few seconds. The quality of these shares tell the mining pool how much work was invested.
When a block is found, the rewards is split among all workers, proportionally to the amount of work they proved.
Put bluntly, Proof of Work is the conversion of electrical power into heat.
All the computing done in a Bitcoin mining operation is worthless, most the obtained results are thrown out and a single winning hash is submitted into the network as the new Bitcoin block. Bitcoin's current network hashrate is at over 80 Quintillion (10 to the 18th power!) hashes per second. Ten with 18 zeroes hashes are computed all over the world each second just to find one Bitcoin winning block which will pay out 12.5 BTC in rewards.
As you can probably guess, a proper mining farm, or Bitcoin factory as some call it, requires a massive power infrastructure.
If we do the math based on the global yearly power consumption, we can arrive at the average wattage per Bitcoin.
Per day, an average of 144 Bitcoin blocks are mined. (One block every 10 minutes = 6 blocks per hour x 24 hours a day.)
That's 52,560 blocks per year.
At 64 Terawatt-hours per year, which is the same as 64,000 Gigawatt-hours per year, we get:
64,000 / 52,560 = 1.22 Gigawatt per Bitcoin block
At today's rate, each block pays 12.5 BTC reward.
So 1.22 / 12.5 = 0,0976 gigawatt per Bitcoin. Same as 97.6 megawatts / BTC.
Any large scale mining operation should then calculate costs based on spending approximately 100 megawatts to mine a single Bitcoin.
Electricity costs vary greatly between states in the USA. Washington kW-h costs 9.95 cents while Hawaiians pay 30.45 cents, roughly 3 times more.
To mine a Bitcoin in Washington State, you'd invest U$ 9950.00 on average (100 megawatts) in electrical power. In Hawaii it'd cost over 3 times more.
At today's U$ 10,500.00 Bitcoin price it'd yield about 10% profit before taxes in Washington. Although most miners don't actually sell their BTC straight away. Provided they have some cash reserve, mined Bitcoin can be held until closer to the next halving when block reward will pay 6.25 BTC / block (and mining will become twice as expensive). Keep in mind that cash flow is a big problem for all large Bitcoin mining farms. Selling some of the produce will be necessary along the way.
Based on the energy cost calculation, we can now estimate what kind of electrical infrastructure we'll need.
We know each bitcoin consumes 100 megawatt-hour on average with data from around the globe.
First question to ask is how much BTC does the mining operation target per day?
Let's assume the goal is to mine one BTC per day. I chose one BTC for the sake of simplicity. Since all these calculations are linear, you can simply multiply or divide by X amount of BTC as needed.
Total power consumption then will be 100 megawatt-hour over a period of 24 hours, which equals 4.17 MW-hour on average (4170 KWh). (That's a lot of energy, something like 1000 x 4.2kw electrical heaters hooked up in parallel.)
4170 KWh means instantaneous 4170 KW is consumed during one hour.
On a 220 Volt line, this means pumping 18,900 amps of current into your mining farm every second of the day.
The largest gauge electrical cables you'll find are about half an inch diameter, which will each carry about 300 amps. So to drive 18,900 amperes, you'll need 63 parallel cables from your main power distribution box over to where you'll derive individual electrical sockets.
If your working voltage is 110V you'll need twice as many cables or around 126 cables.
All this just to mine one single Bitcoin per 24 hours on average.
For comparison, let's take a look at some of the busiest mining farms in the world.
F2Pool, for example, mines on average about 18 Bitcoin blocks per day.
At 1.22 Gigawatt per block (derived earlier), this means F2Pool is consuming about 22 gigawatts of power every day.
BTC.com mined 20 Bitcoin blocks on September 1st 2019. That's 24.4 gigawatts.
ViaBTC mined 9 Bitcoin blocks on the same date. That's 11 gigawatts.
You can check out more mining pools by visiting the Blockchain.com explorer and clicking on the various statistics available.
From the above calculations it's obvious the large farms are not working on 220V or even 480 volt lines. Large scale Bitcoin mining requires a high voltage line to reach as close to the mining operation as possible as to shorten the thick cables needed for transmission.
Ideally, a series of pole pig transformers ("street transformers") should be installed at a safe location in the Bitcoin factory. The low voltage 220VAC lines should come down from it directly, avoiding long thick and expensive cables.
As you can see from large mining operation photos seen around the WWW, thinner cables go from a power distribution center to the individual miners. This is because each miner consumes 1.6 kilowatts maximum. A relatively thin cable can be used for this kind of power.
If the individual miner sockets are placed close to the pole pigs, it's possible to save a lot of money by not deploying expensive low voltage cabling.
A High Voltage supply can be arranged with your local utility company. Prices per kilowatt are usually lower than low voltage lines, but it requires some infrastructure and special safety measures near the high voltage working area.
Bitcoin mining factories are set up to dissipate as much power as possible.
As we mentioned before, mining is basically the conversion of electrical power into heat.
For a one BTC / day mining operation, you'll need to dissipate 4170 kilowatts 24x7 in order to maintain room temperature.
Let's calculate the cubic feet per minute (CFM) of airflow needed to cool a room from 100 degrees Fahrenheit to 73 degrees (about 23 Celcius which is OK operating temp for a miner).
4170 x 1000 x 3.16 / 27 = 488,044 CFM or 829,192 cubic meters per hour
We need 488,044 cubic feet per minute of airflow to keep the hypothetical mining operation going at 23 degrees celcius whenever the temperature reaches 100 degrees Fahrenheit.
For immediate cooling (100% of 488k CFM blowing in one minute) to 23 degrees, over 270 industrial fans would be needed (left picture), but instantaneous cooling is not required for cryptocurrency mining. A 5% duty cycle, or about 10 industrial fans, should be able to keep the factory at 23 degrees. All this depends on the weather in your area. Washington state, which we exemplified earlier, is ideal for mining because of cheap electricity and cold weather.
As you can tell from these figures it's impossible to cool a large mining operation using air conditioners. You'd spend more power on those than on mining itself. Therefore the only way to keep such factories cool is through forced convection. Perhaps that's why miners choose Norway, Iceland, Russia and Northern China so much, after all passive airflow cooling is not a problem there.
Also considering night hours when temperature drops, it is possible to maintain constant 23 degrees using less resources during the night.
So much for cooling the factory, now for the electrical distribution.
Mining farms are organized into rows of miners.
Here's a front view of one such row (photo via Wikipedia):
Each miner consumes between 1.2 and 1.6 kilowatts. The cable going from the main distribution center to each miner should be able to handle at least 42% more current than continuous usage. So, at 110V 1.6 kw means 14,55 continuous amperes. Ideally, you'd buy 20 amp cable (9 AWG).
In the above picture (from Genesis Mining) you can see how neatly all cabling is tied and conducted to the central power distribution via the ceiling.
Miners do not require large bandwidth. The nonces they hunt are tiny little things compared to the amount of bandwidth we spend on music, video and so on.
Each miner requires an ethernet connection to a switch. Each row of miners should have one active device such as a switch, to which all miners in that row will connect and from which you derive one single cable back to the networking gateway.
Each row drives just one networking cable through the duct back to the gateway, that's why you don't see such a mess of network cables in professional mining operations.
The more messy cabling you see, the less professional it is.
Beginners tend to make a mess out of their first mining attempts.
Back in the day you'd have lots of options for your mining hardware. Today you basically only have two.
Bitmain sells Antminers, the most popular miners out there.
Modern Antminers, such as the S17 pictured below yield about 53 TH/s, weigh 11kg and consume about 2385 watts. S17 goes out at U$ 2,727.00 retail suggested price.
According to Coinwarz, the above S17 miner would yield the following results, considering electricity prices of Washington State (9.95 cents / kw).
So an S17 produces about U$ 7.59 per day profit from mining Bitcoin.
The miner would pay for itself after 360 days of continuous operation.
Therefore, using a state of the art Bitcoin miner from Antmain you're looking at about one year before your initial hardware investment is returned.
To produce one Bitcoin per day, you need 810 x Antminers S17 and an initial investment of U$ 2.2 million dollars in mining machines.
Total power consumption for 810 x Antminer S17's would be 1.93 megawatts which is 216% more power efficient than the global average we calculated above of 4.17 megawatt per Bitcoin.
For a professional mining operation you won't need to concern yourself with the mining software.
In fact, you only need to mess with the software if you are a small scale miner.
Antminers come prebuilt and preinstalled and you won't need to do anything to get them running.
Each miner should be set up for proper networking and mining pool specs. Antminer provides special tools to help you set this up at scale.
Other mining hardware providers also offer similar solutions. Your greatest concern in setting up a mining factory is with the facilities, as already discussed.
There are some additional software requirements but they aren't specific to Bitcoin mining. You'll need a control room, a firewall, a network gateway capable of handling the sum of all miner traffic and so on. These are calculated and set up like any other server room and aren't specific to cryptocurrency mining.
In this article we've taken a superficial look at some of the infrastructure needed to mine Bitcoin at a scale.
We performed all calculations using a one Bitcoin per day yield. As you can see, Bitcoin mining is extremely costly and requires massive infrastructure to produce a single coin per day.
All the calculations we performed will double in requirements once Bitcoin halves the block rewards. There's one halving every 4 years approximately, so all these calculations are only valid for a 4 year period at most. Mining hardware also changes very quickly, so your mileage may vary with the available miners at the time you read this. Calculations are linear, so if the rewards halve, then your cost doubles. If miners become twice as efficient, your cost halves and so forth.