CO2 per transaction across grid mixes
Same network energy-per-tx figure, only the electricity source changes. Miners chase the cheapest power, which is often far cleaner or far dirtier than a country's retail grid average.
| Grid mix | kg CO2 / kWh | CO2 per tx | Your total |
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Bitcoin's footprint isn't per-user, it's per-network
Total network energy use is driven by hashrate and block reward, not by how many people transact โ a lightly-used chain at the same hashrate burns the same electricity. For miner-side economics rather than environmental impact, see the mining profitability calculator or hashprice ASIC payback calculator.
Why "CO2 per transaction" is the right number and the wrong number at once
Bitcoin's energy consumption is a function of total network hashrate โ how much computing power is racing to find the next block โ multiplied by how efficient the hardware doing that racing is. It has almost nothing to do with how many transactions are waiting in the mempool. A block with one transaction and a block with three thousand consumes the same electricity to mine, because the proof-of-work difficulty adjusts to hashrate, not throughput. That's why dividing total annual network energy by annual transaction count produces a number โ commonly cited in the hundreds of kWh per transaction โ that is mathematically correct as an average allocation but misleading as a causal statement. It answers "if network energy use were split evenly across every transaction, what would each one cost," not "how much extra energy did my transaction actually cause," which for an already-mining network is close to zero.
The other half of the equation, grid carbon intensity, is where the real variance lives. Mining is famously mobile: operations relocate to wherever electricity is cheapest, and cheap power tends to sit at either extreme โ heavily subsidized coal in some regions, or curtailed hydro, flared associated gas, and stranded renewables that would otherwise go unused in others. Cambridge's CBECI and various mining-council surveys have put Bitcoin's sustainable-power mix estimate anywhere from roughly a third to over half of hashrate, a wide enough band that the honest answer to "how dirty is a Bitcoin transaction" is "it depends heavily on which miners happened to find the blocks your transaction was in" โ not something any single average can settle.
None of that makes the number meaningless. Whatever this year's true carbon intensity of the mining fleet turns out to be, total network energy consumption is real, metered at the grid level even if not at the miner level, and growing roughly in step with the price of Bitcoin, since higher prices draw in more hashrate. Treat the per-transaction figure below as a directional allocation for comparison purposes โ useful for putting Bitcoin's footprint next to a flight, a car trip or a data center โ not as a precise receipt for any single transfer.
FAQ
How is Bitcoin's carbon footprint per transaction calculated? The network's total annualized electricity consumption (estimated by Cambridge CBECI / Digiconomist from hashrate and assumed miner hardware efficiency) is divided by the number of on-chain transactions per year to get an average kWh-per-transaction figure. That figure is then multiplied by a grid carbon intensity (kg CO2 per kWh) that reflects the mix of coal, gas, hydro, nuclear and renewables actually powering the miners. Because mining locations and their energy mix shift over time, both the energy-per-tx and the carbon-per-kWh numbers are estimates, not a metered reading โ this calculator lets you adjust both.
Is the per-transaction carbon footprint a fair way to measure Bitcoin's environmental impact? It's the most commonly cited metric, but it has a well-known flaw: Bitcoin's energy use is driven mostly by total hashrate and block reward, not by transaction count, so if fewer transactions used the same amount of total network energy, the per-transaction figure would rise even though nothing about miner behavior changed. A more accurate framing splits the footprint into a fixed network-wide total (roughly constant regardless of who transacts) and treats the per-transaction number as an average allocation of that shared cost, similar to allocating a payment network's data-center energy across cardholders.
Why does grid carbon intensity change the result so much? The same kWh of mining electricity can produce roughly 15x more CO2 if it comes from a coal-heavy grid (~0.82 kg CO2/kWh) than from a hydro- or renewable-heavy grid (~0.05 kg CO2/kWh). Mining migrates toward the cheapest available power, which is often stranded hydro, flared gas or curtailed renewables rather than the local retail grid mix, so the honest range to model is wide โ this calculator defaults to a global blended average but lets you test both ends.