Current Android devices with smaller screens almost universally have less powerful hardware. A slower CPU, slower GPU and smaller amount of RAM will consume les

Current Android devices with smaller screens almost universally have less powerful hardware. A slower CPU, slower GPU and smaller amount of RAM will consume less energy. They also tend to have lower pixel densities, which usually mean higher light transmission (with LCDs) and therefore less energy spent running the backlight. There's also less area to illuminate.