Ethereum Completed the Merge and Replaced Mining With Proof of Stake

Ethereum completed the Merge on September 15, 2022, replacing proof-of-work mining with proof-of-stake validators while preserving the network’s existing execution state, accounts, smart contracts and transaction history.

The transition occurred after Ethereum’s execution layer reached the predetermined Terminal Total Difficulty of 58,750,000,000,000,000,000,000. Etherscan records block 15,537,394—the first block after the final proof-of-work block—as proposed through Beacon Chain slot 4,700,013 and timestamped at 06:42:59 UTC.

How the transition worked

The Merge joined two systems that had previously operated in parallel. Ethereum’s execution layer continued processing transactions and smart-contract state. The Beacon Chain, which had operated since December 2020 without carrying mainnet transactions, became the consensus layer responsible for selecting block proposers and organizing the canonical chain.

Ethereum developers divided the change into two stages. Bellatrix prepared the Beacon Chain on September 6, 2022. Paris activated on the execution layer when accumulated mining difficulty reached the fixed threshold. The next block was then produced by a proof-of-stake validator rather than a miner.

Completion required more than producing one validator block. The Ethereum Foundation’s contemporaneous protocol announcement defined the transition as complete after the Beacon Chain finalized the first post-threshold block. Coin Metrics reported on September 15 that only one slot was missed during the first two 32-slot epochs and that validators finalized the transition after approximately 13 minutes. Its observations covered the immediate transition window, not long-term network performance.

Why the change mattered

Ethereum altered the mechanism securing a live ledger supporting cryptocurrency transfers, applications and tokenized assets without restarting that ledger or requiring users to exchange their existing ether. Miners competing with computational hardware ceased producing canonical Ethereum mainnet blocks; validators committing staked ETH assumed that role.

That transfer changed Ethereum’s infrastructure economics. Mining depended on specialized computing equipment and continuous electricity expenditure. Proof of stake instead made validator capital, software availability and correct attestations central to block production. The Merge therefore removed Ethereum mainnet’s protocol-level demand for proof-of-work mining, although displaced equipment could be shut down, sold or redirected to other networks.

An event-day Crypto Carbon Ratings Institute study estimated that the change reduced Ethereum’s annualized electricity consumption by more than 99.988%. The calculation compared an August 2022 proof-of-work baseline with proof-of-stake client measurements collected during August and September 2022. It was a modeled network estimate—not a meter reading of every participant—and the researchers said later measurements would be needed as the network evolved.

What the Merge did not change

The Merge was a consensus transition, not an expansion of Ethereum’s transaction capacity. It did not materially lower application gas fees or produce a large immediate increase in layer-one throughput. Accounts, contract addresses and ether balances continued on the same execution ledger.

Staked ETH also remained unavailable for withdrawal on September 15, 2022. The Ethereum Foundation had deliberately excluded withdrawals and other nonessential changes from the upgrade to reduce transition risk. Validator rewards continued accruing on the Beacon Chain pending a separate future network upgrade, while transaction priority fees could be directed to validator-controlled execution-layer addresses.

The event-day conclusion

The verifiable September 15 development was narrower than claims that the Merge had solved Ethereum’s scalability, fee or governance challenges. Ethereum successfully changed its mainnet consensus engine, achieved proof-of-stake finality during the initial observation window and ended proof-of-work block production on the canonical chain.

Longer-term claims about validator concentration, censorship resistance, security or market value required evidence beyond the transition itself. On September 15, the defensible conclusion was that a years-long, multi-client protocol migration had crossed its activation threshold and continued producing finalized blocks without recorded mainnet downtime.