With this first upgrade, the community decided to swap the proof-of-work chain with this proof-of-stake chain upon hitting a certain Total Terminal Difficulty (TTD) value on the original Ethereum blockchain. Previously, the Ethereum blockchain relied on proof-of-work, a consensus mechanism that requires a lot of computational effort from all the decentralized nodes participating in the blockchain. How the upcoming Ethereum Merge could change crypto’s rewards, costs and reputation Which Ethereum-focused startups will survive the Merge? According to the Ethereum Foundation, today transition reduces Ethereum’s energy consumption by 99.95%.