Incandescent light bulbs create light by heating a filament inside the bulb; the heat makes the filament white-hot, producing the light that you see. Halogen light bulbs create light through the same method. Because incandescent and halogen bulbs create light through heat, about 90% of the energy used is wasted to generate heat. To reduce the heat emitted by regular incandescent and halogen bulbs, use a lower watt bulb (like 60 watts instead of 100).
Fluorescent light bulbs use an entirely different method to create light. Both compact fluorescent light bulbs and fluorescent linear tubes only waste approximately 30% of their energy in heat, making them far cooler and more energy efficient than regular bulbs. Fluorescent light bulbs are an ideal choice whenever reducing heat or saving energy is important.