Laptops are much more power-efficient than desktops, using up to 80% less electricity. Typically, laptops use 15 to 60 watts. In contrast, desktops need 60 to 250 watts. Laptops also have smaller power supplies and long battery life. They're made for energy saving.Desktops need a constant power source and lack these energy efficiencies. Desktop CPUs also use more power than those in laptops. This is because they're faster and less focused on saving energy.