The energy debate

Wonder

1. How does a digital ledger consume as much electricity as a mid-sized country?
2. Why do mining companies move hardware across borders to chase power differentials?
3. Is energy expenditure in proof-of-work wasted heat or a necessary cost of security?

Explore

1. Cambridge researchers’ estimates of bitcoin’s annual electricity use have ranged from roughly 100 to about 200 TWh in recent years, rising with hashrate: comparable to the consumption of a mid-sized country. This figure is not static; it fluctuates with network difficulty and hardware efficiency. Estimates vary significantly between studies depending on assumptions about the average energy consumption per terahash and the geographic distribution of mining operations.
2. Critics highlight two primary environmental costs: carbon emissions from fossil-fuel-heavy grids and electronic waste. Alex de Vries has published estimates of bitcoin’s energy use and emissions since 2018, and with Christian Stoll (2021) estimated the electronic waste from short-lived mining machines. The existence of proof-of-stake consensus, which uses far less energy, provides a technical alternative that critics argue should render high-energy proof-of-work obsolete.
3. Defenders counter that the energy cost is the mechanism that secures the ledger. Rewriting recent history requires more hashpower than the rest of the network combined, making attacks economically prohibitive. This energy expenditure converts physical resources into digital scarcity. Without this barrier to entry, the consensus would be vulnerable to cheaper, centralized manipulation or reversal of transactions.
4. Miners operate as mobile industrial entities seeking marginal cost advantages. They gravitate toward cheap hydroelectric power in Canada and Norway, gas that would otherwise be flared in oilfields in Texas and North Dakota, or curtailed renewable energy that cannot reach the main grid due to transmission constraints. Some mining does absorb surplus or otherwise wasted energy, though most hashrate runs on ordinary grid power.
5. This mobility creates a dynamic equilibrium for grids. When electricity prices spike during peak demand, miners can shut down their operations rapidly, providing valuable demand-response services to grid operators in exchange for lower rates or credits. In Texas, miners earn money by curtailing during grid stress, through demand-response and ancillary-service programs and by reselling power bought in advance. Critics counter that these payments are borne by other ratepayers, and point to noise, water use and local price effects near large sites.
6. The renewable share of bitcoin’s energy mix remains contested, with estimates ranging widely between studies. Cambridge’s 2025 industry survey put 52.4% of mining on ‘sustainable’ sources (42.6% renewables plus 9.8% nuclear), with natural gas the largest single source at 38.2%; critics focus on the absolute emissions from the fossil share. The debate persists because the metric of ‘energy consumption’ does not automatically equate to ‘environmental damage’; a TWh from hydroelectric power has a different carbon impact than a TWh from coal.

Key facts

Exercise nine, six, three, one

Fact check

Dates, figures and claims checked against the published sources listed below.

• Cambridge Centre for Alternative Finance, 'The Cambridge Bitcoin Electricity Consumption Index' (ccaf.io)
• A. de Vries, 'Bitcoin's Growing Energy Problem', Joule (2018)
• A. de Vries & C. Stoll, 'Bitcoin's growing e-waste problem', Resources, Conservation and Recycling (2021)