Each proposal to Horizon 2020 or ERC is evaluated by a minimum of 4 remote experts (and it can get up to 10 or more in the case of ERC). The evaluators come from a vast variety of background and expertise from academia, industry, NGOs etc. They undergo a selective screening process before becoming evaluators for Horizon 2020 and ERC. The identity of these experts is kept confidential until the end of evaluation process. Once this process is done the EC publishes the full lists of the experts that have participated in the evaluation process.
Each of the following lists contains the details of all reviewers under a specific theme and year, as follows (source: the EU Research & Innovation Participant Portal)