Image: ShutterstockThe energy consumption of Ethereum before the Merge upgrade in 2022 ranged from 46.31 terawatt hours (TWh) per year to 93.98 TWh per year. The Merge, a highly anticipated blockchain upgrade for Ethereum, reduced the network's energy consumption by an impressive 99.9 percent. On September 15, the Ethereum blockchain switched from proof-of-work (PoW) to proof-of-stake (PoS). This was a move to transition into a more sustainable and eco-friendly blockchain. Since then, there has been a significant decrease in the total energy consumption of the Ethereum network.Ethereum's energy consumption has been increasing steadily over the past few years. In 2019, the average energy consumption was 46.31 TWh per year. However, this number increased to 93.98 TWh per year in 2020. The highest energy consumption was recorded on December 26, 2020, at 4.75 TWh per year.Ethereum's energy usage has dropped by over 99.9 percent since the Ethereum Merge on September 15th. The network's carbon footprint is currently at 0.1 million tonnes of CO2 (MtCO2) per year. The electrical consumption for a single Ethereum transaction is very low, at just 0.03-kilowatt hour (kWh). This means that the carbon footprint for a single transaction is also very low, at just 0.01 kgCO2. This is equivalent to the energy used when watching two hours of YouTube, according to a digiconomist. Despite Ethereum's transition to Proof of Stake (PoS) celebrations, community members have raised concerns about the blockchain's centralisation and increased regulatory scrutiny. After the Merge, it was clear that centralisation was a problem. 46.15 percent of the nodes responsible for storing data, processing transactions, and adding new blockchain blocks were attributed to just two addresses.RA Wilson, chief technology officer of crypto and carbon credits exchange 1GCX, believes that the 'Merge has enabled large holders of Ether to gain mass control of the network.' This makes it significantly more centralised and certainly less secure. He further explained:“Many ETH holders stake their crypto on centralized exchanges such as Coinbase, which allows these platforms to become dominant holders on the network, contributing to stakeholder centralization.” Shashank is founder at yMedia. He ventured into crypto in 2013 and is an ETH maximalist.