Green Coins: How Digital Money Learned to Save Energy

Remember the chain-of-trust notebook, guarded by thousands of computers? Here's a secret: guarding it takes electricity. Sometimes a LOT of electricity.

The racing problem

The first digital money, Bitcoin, keeps its notebook safe with a giant race. Millions of computers all race to solve a puzzle, over and over, all day long. The winner adds the next page. Racing keeps cheaters out — but all those racing computers together use as much electricity as a whole country. That's a lot of power for a notebook!

And our planet is working hard to use less energy from smoky fuels, not more. So clever engineers asked: can we keep the notebook safe without the race?

Taking turns instead of racing

They found a way. Instead of millions of computers racing, the computers take turns — and to take a turn, you must promise something valuable, which you lose if you cheat. No racing means almost no wasted energy.

When the second-biggest digital money, Ethereum, switched from racing to taking turns, its energy use dropped by more than 99%. Imagine a thousand hair dryers running all day — and then switching to just one tiny night-light. That's how big the saving was!

Chains that help the planet

Now people are using chains of trust for the Earth: tracking where our food travels, proving that solar energy is really solar, and making sure promises to plant trees are actually kept.

Three tomorrows

• 🟢 Green tomorrow: Digital money runs on tiny amounts of clean energy and helps us track and protect nature.
• 🟡 Yellow tomorrow: Some chains go green, others keep racing and using too much power.
• 🔴 Red tomorrow: Energy-hungry racing grows and grows, and the planet pays the bill.

Try it: Tonight, count the screens in your home. Every screen uses energy — and so does invisible computer money. What's one way your family could save a little energy tomorrow?