Ethereum is the most popular blockchain network because of the introduction of a smart contract. While Ethereum-based software has significantly increased in the wake of their popularity, the carbon emitted by them is pointed to as a global issue.To reduce the emission of carbon, it is necessary to reduce the energy consumed by the software. Recently, most studies have focused on the smart contract and then proposed energy efficiency methods for carbon friendly Ethereum networks. However, it is required to review not only smart contract but also client software for energy used in Ethereum network. This is because the client software performs all functions occurring in Ethereum network that includes smart contracts. Therefore, we need to investigate energy bugs that waste energy in the Ethereum client software, and then study to solve these bugs. The first task to make these studies possible is to build the energy bug benchmark of Ethereum client software. This paper introduces ECench, an energy bug benchmark of Ethereum client software. ECench includes 507 energy buggy commits from 7 series of client software that are nomally operated in Ethereum network. We carefully collected and manually reviewed them for the more clean commits. Another key strength of our benchmark is to provide the 8 categories which cause energy wastage. These categories can serve as a cornerstone for researchers to identify energy waste codes. Consequently, it can provide a valuable starting point for studies for energy reduction, further carbon reduction, in Ethereum.