The claim that a microwave's clock uses more power in the microwave's lifetime than the power required to heat food is a common misconception, but it is not accurate. In reality, the power consumed by a microwave's clock is negligible compared to the power used for heating food.
A microwave's clock is a simple electronic component that requires very little energy to operate. It usually consumes only a few watts or even less. On the other hand, the power used for heating food is substantially higher, typically ranging from hundreds to over a thousand watts, depending on the microwave's wattage and the cooking time.
When you use a microwave, the vast majority of the energy consumption goes towards generating microwaves that cook the food, not towards powering the clock. As a result, the energy used by the clock over the lifetime of the microwave is significantly lower compared to the energy used for cooking.
While it's always a good idea to conserve energy where possible, worrying about the clock's power usage is not a significant factor in the overall energy consumption of a microwave. If you want to be more energy-efficient when using a microwave, focus on minimizing the cooking time and avoiding unnecessary preheating or using higher power settings than required.