Ethereum will use an estimated 99.95% less energy post merge

TLDR: Under PoW, as the price of ETH and the hashrate are positively correlated. Therefore, as as the price increases, in equilibrium so too does the power consumed by the network. Under Proof-of-Stake, when the price of ETH increases, the security of the network does too (the value of the ETH at-stake is worth more), but the energy requirements remain unchanged.

Source: https://blog.ethereum.org/2021/05/18/country-power-no-more/