Crypto's environmental impact and energy use

What the best estimates say, what they can't tell you, and why the answer differs so much between Bitcoin and Ethereum.

Why some crypto uses so much energy

Bitcoin is secured by proof of work. Miners run specialized machines (ASICs) that make trillions of guesses per second to find a valid block, and the network adjusts the difficulty so a block is found about every 10 minutes however much computing joins in. Energy use is a feature of this design, not a bug: to rewrite Bitcoin's history, an attacker would have to outspend all of that electricity. The more valuable the reward, the more miners are willing to spend, so energy use tends to follow the price of bitcoin and the cost of power.

It also means a single transaction doesn't "use" a fixed amount of energy. The network burns roughly the same power whether blocks are full or empty, so per-transaction figures you see online are averages that can mislead.

How much electricity Bitcoin uses

For scale, 138 TWh is in the range of a mid-sized country's yearly electricity use. Cambridge's live index, the Cambridge Bitcoin Electricity Consumption Index (CBECI), gives a lower and upper bound as well as a best guess, because no one can see every miner's machines and power bills. It estimates from the network's total computing power (hash rate) and the efficiency of the machines likely in use. Treat any single number as an estimate with a wide margin.

The energy-mix debate

How harmful the electricity is depends on where it comes from, and this is where people disagree most.

The case that it's getting cleaner

• In Cambridge's 2025 survey of miners, renewables plus nuclear made up about 52.4% of mining's power. The preliminary 2026 update raised that to 59.4%, with hydropower overtaking natural gas as the largest single source.
• Miners can switch off in seconds, so some sign deals with grid operators to cut demand during peaks, and some use energy that would otherwise be wasted: gas flared at oil wells, or surplus hydro and wind power far from cities.
• After China's 2021 mining ban pushed out coal-heavy operations in some provinces, the industry relocated to places with different power mixes.

The case for concern

• The 2025 survey covered about 48% of global hash rate (the 2026 update a little over half), and miners who volunteer data may be the cleaner ones. Cambridge itself flags this limitation.
• Natural gas and coal still supplied a large share (gas was the biggest single source in the 2025 report), and emissions rose in the 2026 update as total consumption grew.
• Average shares can understate the impact of extra demand: a new mine on a grid may keep a fossil plant running longer even if the grid is partly green.
• Local effects matter: noise, water use for cooling and higher power prices have caused disputes in towns near large mines.

Both sides can cite real data. The honest summary is that Bitcoin's footprint is significant, uncertain, and depends heavily on local power sources.

Ethereum's Merge: a 99.95% cut

Ethereum used proof of work until September 15, 2022, when "the Merge" switched it to proof of stake. Instead of mining, validators lock up ether as a deposit and are chosen to propose and check blocks; misbehaving can cost them part of that deposit. Ordinary computers can do this work, so the energy race disappeared. The Ethereum Foundation estimates the change cut Ethereum's energy use by about 99.95%, to an estimated 2.6 gigawatt-hours a year, roughly what a few hundred US homes use.

Most networks launched since then use proof of stake. Bitcoin's community has shown no interest in switching, because many of its users see proof of work's cost as the source of its security and neutrality.

Proof of work vs. proof of stake

Electronic waste

Bitcoin mining machines do one job, and newer models quickly make older ones unprofitable. A 2021 study by Alex de Vries and Christian Stoll estimated Bitcoin produced about 30.7 thousand tonnes of electronic waste a year as of May 2021, about as much small IT waste as the whole of the Netherlands produces, on the assumption that a mining machine is used for only about 1.3 years. Others argue machines now last longer and are resold to regions with cheaper power. Either way, unlike a laptop, an obsolete mining chip can't be reused for anything else.

What's being done

• Disclosure. The EU's MiCA law requires crypto white papers and service providers to disclose the climate impact of a coin's consensus mechanism. See EU crypto rules.
• Local limits. New York passed a two-year moratorium in 2022 on new permits for fossil-fuel plants powering proof-of-work mining; some Canadian provinces rationed power for mining. China banned mining outright in 2021.
• Industry choices. Miners increasingly locate near cheap surplus power, reuse waste heat, or run on flared gas; critics say these are a small share of the total.
• Choosing networks. If energy is your main concern, the gap between proof-of-work and proof-of-stake networks is enormous. See what is crypto mining.

Related reading: ASIC vs. GPU mining, and how mining pools pay · Consensus mechanisms: how blockchains agree

Frequently asked questions

Where to next

Sources

1. Cambridge Bitcoin Electricity Consumption Index (Cambridge Centre for Alternative Finance)
2. Bitcoin power use jumps 38% with greener energy mix: Cambridge update (The Energy Mag, 2026)
3. Tracking electricity consumption from US cryptocurrency mining operations (US Energy Information Administration, February 2024)
4. Ethereum energy consumption (ethereum.org)
5. The Merge (ethereum.org)
6. Bitcoin's growing e-waste problem: de Vries and Stoll, Resources, Conservation and Recycling 175 (2021)

Written for beginners and checked against the sources listed. Last reviewed November 4, 2026. This page is educational and is not financial, tax or legal advice. How we write and check pages.