When you send Bitcoin or trade Ethereum, you might think it’s just a digital transaction-no wires, no factories, no fuel. But behind every block added to the chain is a real, measurable cost: energy. And that cost is growing, fast.

Bitcoin alone uses more electricity annually than most countries. In 2025, estimates range from 175 to over 211 terawatt-hours (TWh) per year. That’s more than the entire power usage of Thailand or Vietnam. It’s equivalent to running 20 million homes nonstop. And while that number sounds terrifying, it’s not the whole story. Not all blockchains are built the same. Some use nearly zero energy. The real question isn’t whether blockchain is bad for the planet-it’s which kind of blockchain you’re talking about.

Why Bitcoin Uses So Much Power

Bitcoin runs on something called proof-of-work (PoW). To add a new block, miners compete to solve incredibly hard math puzzles using powerful computers. The first one to solve it gets rewarded in Bitcoin. The harder the puzzle, the more electricity it takes. And as more miners join, the puzzles get harder-creating a never-ending arms race for more computing power.

Each Bitcoin transaction consumes about 1,375 kilowatt-hours (kWh) of electricity. That’s enough to power an average U.S. home for over a month. Compare that to a single Visa transaction, which uses about 0.0001 kWh. One Bitcoin transaction equals over 1 million Visa payments in energy use.

The reason? Bitcoin’s design prioritizes security and decentralization over efficiency. It can only process 7 transactions per second. To handle more, you’d need bigger blocks or faster blocks-but that weakens security. So instead, Bitcoin doubles down on computational power. More miners. More machines. More electricity.

The Ethereum Game-Changer

In September 2022, Ethereum-once the second-largest energy guzzler in crypto-pulled off what many thought was impossible. It switched from proof-of-work to proof-of-stake (PoS). This change, called “The Merge,” cut its energy use by 99.99%.

Before the Merge, Ethereum used about 74.6 TWh per year. After? Just 0.0026 TWh. That’s less than a small town. No more mining rigs. No more spinning hard drives. Instead of solving puzzles, validators lock up 32 ETH (about $56,000 in 2023) as collateral to propose and verify blocks. If they cheat, they lose their stake. It’s like a digital notary system powered by economics, not electricity.

For users who care about sustainability, this was a turning point. Reddit threads exploded with celebration. CryptoSlate’s 2025 survey found 68% of users now consider energy efficiency a top factor when choosing a blockchain. Ethereum’s shift didn’t just save power-it proved that blockchain could evolve.

How Other Blockchains Stack Up

Bitcoin isn’t alone in its energy hunger. But many newer blockchains were built differently from day one.

• Cardano: Uses PoS. Consumes 0.006 TWh per year-equal to two small power plants.
• Algorand: Pure PoS. Uses just 0.0002 TWh annually. That’s about the same as 200 U.S. homes.
• Nano: Uses a block-lattice system with no miners. Each user validates their own transactions. Energy per transaction: 0.000112 kWh.
• Tezos: Also PoS. Uses 0.000128 TWh per year.
• Polkadot: Uses a hybrid consensus model. Estimated at 0.0008 TWh per year.

These aren’t theoretical numbers. They’re measured by independent researchers at Cambridge and Digiconomist. The difference between Bitcoin and Cardano? Cardano uses less than 0.003% of the energy Bitcoin does. That’s like comparing a jet engine to a bicycle.

The Renewable Energy Myth

Bitcoin supporters often point to renewable energy. The Bitcoin Mining Council claims 56% of its network runs on renewables-mostly hydro in China and wind in Texas. That sounds good. But here’s the catch: “renewable” doesn’t mean “zero impact.”

Hydroelectric dams flood valleys. Wind turbines need rare earth metals and disrupt wildlife. And when the wind dies down or the river dries up, miners switch back to coal or gas. There’s no guarantee the energy is new or additional. It’s often just using excess power that would’ve been wasted anyway.

Meanwhile, Cardano’s foundation claims most of its validators use green energy. But independent audits in 2025 found only 37% of its top 50 stake pools disclosed their energy sources. Transparency is the issue-not the technology.

Using renewable energy doesn’t fix the fundamental problem: PoW still needs massive amounts of electricity, even if it’s clean. PoS doesn’t need much at all-even if it runs on coal.

Regulation Is Catching Up

Governments aren’t waiting for the market to fix this.

In 2023, New York State banned new Bitcoin mining facilities. That ban is still active through December 2025. The European Union’s MiCA regulation, effective January 2025, forces all blockchain platforms operating in Europe to publicly report their energy use. Singapore launched a $150 million fund to support low-energy blockchain projects. The UN is even discussing a global mining levy-essentially a carbon tax on crypto.

And it’s working. Fidelity’s 2025 report shows 82% of enterprise blockchain deployments now use PoS or similar low-energy systems. In 2020, that number was just 19%. Companies don’t want to be accused of greenwashing. They want compliance. And compliance means ditching PoW.

What’s Next for Crypto’s Energy Future

Dogecoin is planning its own PoS switch in 2026. If it succeeds, it could cut global crypto energy use by another 12 TWh-roughly the output of 10 large power plants.

Projects like Filecoin are experimenting with AI to optimize energy use across decentralized storage networks. The idea? Use smart algorithms to run mining tasks only when renewable energy is abundant. But there’s a risk: AI itself could consume more power than Bitcoin by the end of 2025, according to Cambridge research.

Some experts believe Bitcoin’s energy use will stabilize around 200-220 TWh per year as mining hardware gets more efficient. Others predict PoW blockchains will make up less than 5% of crypto’s market cap by 2030. Bloomberg Intelligence says the writing is on the wall. The era of energy-hungry blockchains is ending.

The most optimistic view? That blockchain technology could reach net-zero emissions by 2035-if every mining operation switches to renewables and every new chain uses PoS. But that’s a big “if.” Right now, only 56% of Bitcoin mining uses renewables. To hit net-zero, you’d need over 90%.

What You Can Do

If you’re using crypto, you have more power than you think.

• Choose PoS chains like Ethereum, Cardano, or Algorand over Bitcoin or Litecoin for everyday transactions.
• Ask wallet providers and exchanges which blockchains they support and how much energy they use.
• Don’t assume “crypto” means Bitcoin. Most newer projects are built to be sustainable.
• If you’re a developer, learn PoS. Ethereum’s transition took over 1,200 code commits and six years. The next generation needs to start now.

The environment doesn’t care about decentralization or immutability. It only cares about energy use. And right now, the cleanest blockchain is the one that doesn’t need to mine at all.