Computer Configuration > Administrative Templates > Microsoft Edge > Sleeping tabs settings
Both
HKLM\Software\Policies\Microsoft\Edge
This policy setting lets you configure whether to turn on sleeping tabs. Sleeping tabs reduces CPU, battery, and memory usage by putting idle background tabs to sleep. Microsoft Edge uses heuristics to avoid putting tabs to sleep that do useful work in the background, such as display notifications, play sound, and stream video. By default, sleeping tabs is turned on. Individual sites may be blocked from being put to sleep by configuring the policy 'SleepingTabsBlockedForUrls' (Block sleeping tabs on specific sites). If you enable this setting, sleeping tabs is turned on. If you disable this setting, sleeping tabs is turned off. If you don't configure this setting, users can choose whether to use sleeping tabs.