Computer Configuration > Administrative Templates > Microsoft Edge > Performance
Both
HKLM\Software\Policies\Microsoft\Edge
Enables efficiency mode which helps extend battery life by saving computer resources. By default, efficiency mode is enabled for devices with a battery and disabled otherwise. If you enable this policy, efficiency mode will become active according to the setting chosen by the user. You can configure the efficiency mode setting using the 'EfficiencyMode' (Configure when efficiency mode should become active) policy. If the device does not have a battery, efficiency mode will always be active. If you disable this policy, efficiency mode will never become active. The 'EfficiencyMode' and 'EfficiencyModeOnPowerEnabled' (Enable efficiency mode when the device is connected to a power source) policies will have no effect. If you don't configure this policy, efficiency mode will be enabled for devices with a battery and disabled otherwise. Users can choose the efficiency mode option they want in edge://settings/system. Learn more about efficiency mode: https://go.microsoft.com/fwlink/?linkid=2173921