Energy-efficient light bulbs. Assortment of energy-efficient (low energy) light bulbs. These light bulbs use a process similar to that in fluorescent tubes, rather than the simple glowing filament of conventional bulbs. These bulbs are up to five times more efficient at converting electricity into light. Therefore, for a given light output, the bulbs use far less electricity. Although more expensive than traditional bulbs, these designs last far longer, providing an overall saving.