Where crypto's carbon comes from
Almost all of it is electricity. Bitcoin is secured by mining: machines around the world race to solve a puzzle, and the winner of each block, about every ten minutes, is paid in newly created bitcoin plus the fees users attach to their transactions. The more bitcoin is worth, the more machines it pays to run, so the network's electricity use follows the price and the reward, not the number of transactions. On 30 October 2026 the network was running at about 1,048 exahashes a second, a record level, according to mempool.space.
Most other large coins, including Ethereum since September 2022, use proof of stake instead: holders lock up coins to vote on blocks, with no race to win, so the network runs on ordinary servers. That is why the carbon question in crypto is mostly a bitcoin question.
Bitcoin's footprint, two estimates
| Cambridge (CCAF) | Digiconomist | |
|---|---|---|
| Electricity a year | 138 TWh | 204.44 TWh |
| Emissions a year | 39.8 MtCO2e | 114.03 Mt CO2 |
| Implied grams per kWh | 288 | 558 |
| Per new bitcoin mined | 242 t CO2e | 694 t CO2e |
| Per bitcoin held for a year | 1,97 t CO2e | 5,64 t CO2e |
| Дата | 28 април 2025 г. | read 30 October 2026 |
The Cambridge Centre for Alternative Finance (CCAF) at Cambridge Judge Business School surveyed mining firms covering 48% of global activity for its Cambridge Digital Mining Industry Report. It found 52.4% of their electricity came from sustainable sources (42.6% renewables, 9.8% nuclear), natural gas had overtaken coal as the largest single source at 38.2%, coal was down to 8.9%, and the United States hosted 75.4% of the activity reported. It put the network at 138 TWh a year, about 0.5% of the world's electricity. CCAF's live index notes that its daily emissions figures still use a January 2022 power mix and probably overstate emissions by about 43%, which is why we use the survey figure.
Digiconomist, run by the researcher Alex de Vries-Gao, estimates consumption from what miners earn and assumes a larger share of fossil power. Its index read 204.44 TWh and 114.03 Mt CO2 a year on 30 October 2026.
The per-bitcoin rows are our own arithmetic on those totals and the Bitcoin blockchain: 3.125 new bitcoin per block and 144 blocks a day is 450 a day, and 20,105,594 bitcoin existed at block 973,789. The crypto carbon calculator does the same sums for any amount.
Three ways to put a number on an amount of bitcoin
- Mining it. The network's emissions for the time it takes to create that many new coins. Useful for scale ("the bitcoin in this story took 40 days of the world's mining"), not for a company report, because the coins were mined once and are then held and traded many times.
- Holding it. A yearly share of the network's emissions in proportion to the share of all bitcoin you hold. This is the method proposed for company carbon accounts; read how to report crypto holdings in a carbon footprint.
- Moving it. A share of emissions for each transaction. Dividing the whole network by its transactions gives a very large figure per transaction; the hybrid method gives transactions only the part linked to fees, under 1% of miners' income in the last year.
Ethereum and the other coins
Ethereum switched from mining to proof of stake on 15 September 2022, an event known as the Merge. The Crypto Carbon Ratings Institute's report for ConsenSys put Ethereum's electricity use at about 22.9 TWh a year before the switch and about 2,600 MWh a year after it: a 99.988% drop in electricity and 99.992% in emissions. Other proof of stake networks are in the same low range. Coins that are still mined, such as Litecoin, Dogecoin and Bitcoin Cash, have the same kind of footprint as bitcoin, in proportion to how much mining they attract; we will add pages for them as we check the figures.
Rules that ask for these figures
In the EU, the markets in crypto-assets regulation (MiCA) makes crypto firms publish each coin's energy use, and for exchanges and trading platforms its greenhouse gas emissions, on their websites. In the UK, no rule makes a company report the footprint of crypto it holds. The detail, and how a company could report it anyway, is in our guide to reporting crypto holdings.
Как помага Carbon Recycling
Carbon Recycling works out a company's Scope 1, 2 and 3 footprint from bills, mileage, travel and spending with the UK government factors, with the method behind every line. Crypto is not in the government factors, so use the free calculator for the holdings figure and report it with its method alongside.