Guaranteeing Resilient Installations for Defense Act of 2020 or the GRID Act of 2020 This bill directs the Department of Energy (DOE) to carry out a two-year pilot program under which DOE must implement mitigating actions to address vulnerabilities assessed at critical defense facilities and their associated defense critical electric infrastructure, after consultation with, and with the consent of, the owners of such infrastructure. DOE shall identify, designate, and mitigate vulnerabilities at facilities located in any state that are (1) critical to the defense of the United States, and (2) vulnerable to a disruption of the supply of electric energy provided to such facility by an external provider.