From w3ctag/design-reviews#626 (comment)

Power consumption is a concern. While there is a mechanism to allow applications to request a high power vs low power device, we are wondering if the choice should be initiated by the user, and not the application. e.g. if the user is on the go, let them choose integrated GPU instead of discrete to save power. Initially, we discussed the possibility of forcing the application to integrated in low-power scenarios, but adds another fingerprinting surface so we don't think this is a valid suggestion.