Gas discharge lamp
Gas-discharge lamps have a long life and a high efficiency, but they are more complicated to manufacture, which makes them more expensive to buy than incandescent lamps. Due to their greater efficiency, gas-discharge lamps replacing incandescent light bulbs for many purposes in the late 20th century. Early in the 21st century, light-emitting diodes improved, with even higher efficiency. They began to replace some gas discharge lamps.