Replacing an incandescent light bulb with a compact fluorescent light bulb (CFL) or light-emitting diode (LED) once was merely a good idea; now, it’s the law. The U.S. has banned the sale of incandescent bulbs after 2012, making energy-saving CFLs and LEDs the bulbs of choice—for the time being.

CFLs lower energy costs by up to 75% and burn about 10 times longer than incandescents, although they contain mercury, which makes disposal a bear. In addition, some consumers claim CFLs don’t last as long as claimed.

LEDs, on the other hand, burn almost 50 times longer than incandescents and up to 6 times longer than CFLs, contain no mercury, and produce one-tenth the carbon dioxide emissions that CFLs produce. They also turn on instantly, where CFLs take time to heat up.