If you aimed for similar class (ultraportable), you're going to be in pretty much the same ballpark. Ultraportable CPUs are normally in the sub 15W (peak) now,

If you aimed for similar class (ultraportable), you're going to be in pretty much the same ballpark. Ultraportable CPUs are normally in the sub 15W (peak) now, and screens are The embodied energy of the laptop is high (estimate in the ~5GJ range) (http://conferences.sigcomm.org/hotnets/2011/papers/hotnetsX-final56.pdf http://conferences.sigcomm.org/hotnets/2011/papers/hotnetsX-...). Ballparking now... assuming 5GJ of embodied energy, 20W power draw, 100% duty cycle, you'll need to run a laptop for about 8 years for its power draw to match its embodied energy. That means that changing laptops much more frequently than that will probably result in net higher energy consumption. Obviously, the lower the power consumption gets, the longer the "payoff" period becomes - this is why servers which might have 10x the embodied energy, but >40x the power draw are still economical to have more rapid hardware refresh cycles.