Bitcoin has been alarming people for years because of the amount of electricity needed to mint new virtual coinage.

Bitcoin and most other cryptocurrencies are founded on the notion of an immutable ledger, called the blockchain, which comprises the transfer of value from one party to another.

Cryptocurrency “miners” seek results to a kind of algorithmic puzzle that fits a very specific set to requirements. Every ten minutes on average, a server finds an acceptable solution, and the miner gets a reward from the bitcoin system.

The miner’s combination of solution and transactions is also added to the blockchain. The new block does not become a de facto part of the ledger until a few more blocks are added, because valid solutions are sometimes found simultaneously, and it is not always clear straightaway which will become the longest, winning fork in the chain.

To ensure that coins cannot be minted too quickly, as the overall network’s computational power increases, the bitcoin protocol continually makes it harder to find a putative solution. Miners are obliged therefore to keep upgrading in order to earn rewards as fast as competitors. And more computing power requires more electricity.