The answer for this one makes a lot of sense. First, it shouldn’t strike you as odd that heating food requires more than 100 times more energy than running the clock. So how exactly does the clock use more energy? It’s simply because of the amount of time spent using a microwave versus the amount of time the microwave is idle. Most microwave ovens are in “standby” mode more than 99% of the time. The same goes for other devices like DVD players, stereos, and coffee machines, though all to different effects of energy usage. The fact remains that a huge amount of power is used on devices in standby mode. So it’s not that the clock uses more energy than the microwave function per hour of use, but that the microwave is in use so infrequently that the energy spent powering the clock is more than those few daily instances of the microwave.
In 1998, it was estimated that standby power accounted for 5% of total electricity consumption in America. Alan Meier, a staff scientist at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California, believes that with improvements in technology and energy consumption, the use of standby energy can be reduced by 72%.