How proof of work secures ordering, why miners compete and where revenue and costs come from.
Follow the mining loop from candidate block to accepted proof of work.
The mining job
Miners build candidate blocks from valid transactions and search for a header hash below the network target. The search is costly; verification by nodes is quick. This asymmetry makes history expensive to rewrite. <strong>Revenue and competition.</strong> A successful block can claim the current subsidy and included transaction fees.
Hardware, electricity, cooling, financing and pool fees compete against volatile revenue, making mining an industrial risk business rather than automatic passive income. <strong>Difficulty adjustment.</strong> Every 2,016 blocks, the protocol adjusts the proof-of-work target based on elapsed time. More global hash rate does not create bitcoin faster over the long run; difficulty rises to keep average block intervals near ten minutes.
<strong>Pools and decentralization.</strong> Pools coordinate many miners and distribute variable rewards more smoothly. They can influence transaction selection, but individual operators can change pools, and nodes still reject invalid blocks.
What this establishesMining makes block creation costly and verification cheap.
Model one machine before buying it
A miner's revenue depends on its share of network work, the subsidy and fees in blocks, uptime, and bitcoin's market price. Costs include the machine, electricity, cooling, pool fees, repairs, financing, and the value of the space used. A calculation using only the device's advertised hashrate and today's price omits most of the decision.
Difficulty can rise while the machine's efficiency stays fixed, reducing expected bitcoin output. Run several cases instead of one forecast: lower price, higher difficulty, reduced uptime, and a more expensive power rate. State whether taxes and resale value are included. Then compare the result with simply buying bitcoin.
Mining can be rational where energy, heat use, operations, and financing fit together, but a profitable snapshot is not evidence that the investment remains profitable over the machine's life.
What this establishesDifficulty targets a stable long-run issuance pace.
The mining loop
A miner assembles a candidate block: the transactions paying the highest fee rates from its mempool, a coinbase transaction paying itself the subsidy plus those fees, and a header. It then hashes the header repeatedly, changing the nonce and other fields, looking for a result below the difficulty target.
Modern machines perform on the order of a few hundred trillion hashes per second each; the network as a whole performs hundreds of exahashes. Finding a valid hash is pure chance, so a miner's expected share of blocks equals its share of the network's hashrate, and pools exist to smooth that lottery into steady income.
What this establishesProfit depends on operational costs and market conditions.
Hardware, energy and location
General-purpose computers stopped being competitive in 2013; application-specific chips that do nothing but SHA-256 dominate, with efficiency measured in joules per terahash improving each generation. Electricity is the dominant running cost, so mining concentrates where power is cheapest: hydro-rich regions in season, gas that would otherwise be flared, grids with surplus off-peak generation, and industrial contracts that pay miners to switch off at peak.
Since China's 2021 ban the largest measured share has been in the United States. The mining dashboard and profitability calculator on this site show the current hashrate, difficulty and the margins those inputs imply.
What mining secures and what it costs
Proof of work makes rewriting history expensive: to reverse a transaction six blocks deep, an attacker would need to out-work the entire network for over an hour. It also decides who issues new coins without anyone being in charge.
The cost is electricity - the Cambridge index estimates annual consumption in the range of a mid-sized country, with wide error bars depending on hardware assumptions. Whether that is wasteful depends on what the security is worth, and the honest position is that both the consumption and the value it secures are measurable while the comparison is a judgement.
Separate the fixed rule from the changing business
The subsidy schedule and difficulty adjustment follow consensus rules. Hashrate, hardware efficiency, power cost, pool terms, and bitcoin price change. A mining claim should say which side of that line it describes.
Questions about mining operations
What do miners actually do?
They gather valid transactions into a candidate block and repeatedly hash its header until the result falls below the network's difficulty target. The first to succeed broadcasts the block and collects the subsidy plus fees, and the process starts again on top of it.
Can I mine bitcoin at home?
Technically yes, but purpose-built ASIC machines dominate, and profitability depends on electricity price, hardware cost and the current difficulty. Most home mining today is done for learning or heat rather than income; the mining profitability tool models the numbers.
What is the block reward?
The subsidy of new coins - 3.125 BTC per block since April 2024 - plus all the fees paid by transactions in the block. The subsidy halves every 210,000 blocks, so fees are expected to carry a larger share of miner income over time.
Sources and further reading
Primary documents this guide draws on. Links open the original publisher.
- Developer guide: mining developer.bitcoin.org
- Mining Bitcoin Wiki
- Difficulty Bitcoin Wiki
- Cambridge Bitcoin Electricity Consumption Index Cambridge Centre for Alternative Finance