Professor Andrew Urquhart is Professor of Finance and Financial Technology and Head of the Department of Finance at Birmingham Business School (BBS).
This is the ninth installment of the Professor Coin column, in which I bring important insights from published academic literature on cryptocurrencies to the Decrypt readership. In this article, I discuss Bitcoin energy usage, and the future for sustainable cryptos.
When you hear the words “Bitcoin mining,” you might picture giant warehouses packed with whirring computers, gobbling up electricity like there’s no tomorrow. That image isn’t far from reality.
Since Bitcoin launched in 2009, its proof-of-work (PoW) system has been both its greatest strength and its biggest controversy. It keeps the network secure and decentralized, but it also ties digital finance to very real energy and environmental costs.
Professor Coin: What Gives Bitcoin Its Value?
The go-to benchmark is the Cambridge Bitcoin Electricity Consumption Index (CBECI), which estimates that Bitcoin mining consumes electricity on the scale of mid-sized countries. But here’s the catch: Bitcoin’s energy use doesn’t rise smoothly. Instead, it follows market cycles. When Bitcoin’s price surges, miners switch on more rigs, pushing up hashrate, difficulty, and electricity demand. When prices dip, older or less efficient machines go dark.
Stoll, Klaaßen and Gallersdörfer (2019) pegged annual consumption around 46 TWh back then, with ~22 megatons of CO₂ emissions More recently, new data suggests that consumption has grown substantially.
According to the 2025 Cambridge Digital Mining Industry Report, Bitcoin’s annual electricity usage is now estimated at 138 TWh, with network-wide emissions of approximately 39.8 Mt CO₂e. The same report also notes that 52.4 % of the energy used by miners comes from sustainable sources (renewables + nuclear) as of 2025.
These updated figures help us see that while Bitcoin’s environmental footprint remains significant, the composition of its energy mix is also shifting—offering a more nuanced narrative for 2025.
How Much Energy Does Bitcoin Really Use? Less Than You Might Think
New research asks a broader question: what’s the total environmental cost? A 2023 paper by Chamanara et al. (2023) estimates Bitcoin mining at ~173 TWh, adding in CO₂, water, and land impacts.
Meanwhile, the UN University warned that mining draws heavily on freshwater in regions with scarce supply. And it’s not just the running of machines: de Vries (2021) estimated tens of kilotons of e-waste annually from discarded ASIC rigs, since miners churn through hardware every couple of years. This holistic picture means Bitcoin’s footprint is now seen as multi-dimensional: electricity, emissions, water, land, and waste.