Plants do not move. Movements in a plant are at the cellular level. In a large plant body, there are many dead cells like schlerenchyma which are not involved in cellular function but provides strength to the plot .As a result it requires less energy.
Animals , on the other hand need more energy to move from one place to another, in search of food and other activities, i.g., mating predation, shelter , etc. So ,the energy need is higher in them.
