If you use a light bulb with a wattage lower than the recommendation for your light fixture, you can expect less light output. However, it will not harm the fixture because of using a lower wattage bulb. "Technology improvements are constantly occurring, which provide greater light while using lower energy," says Knopfler. "It is much more accurate to look at the lumen output than the wattage." Keep in mind that using a bulb with a greater wattage than the fixture's rating is a safety hazard.