Compact Fluorescent Lamp (CFL) is widely popular lighting system in India. These bulbs or tubes contain mercury (in the form of vapor) inside the bulb/tube, an inert gas (majorly Argon) and the surface of the bulb is coated with phosphorous (ex: tube lights). So when electricity passes between the cathode and anode inside the bulb, a chemical reaction is induced and produces ultraviolet light and heat. The color of the light changes depending on the inert gas inside the bulb. To produce different colors of the spectrum, many CFL bulbs are filled with different inert gases in different proportions to produce required colors. The Light produced by CFL bulbs have a longer wavelength. If you are familiar with wavelength and energy, you might know that energy and wavelength are inversely proportional. Hence the energy efficiency of CFL bulbs is very less compared to LED.
Light Emission Diodes or LED's produce light without the intervention of a chemical reaction or need of any gas or mercury vapor. LED's have semiconductors which produce light when electrons travel from anode to cathode. The name itself indicates that it is a diode which emits light when electricity passes through it. Since the electrons move constantly the emitting diodes will emit light with an average lifespan of 50,000 hours. LED's emit light in shorter wavelength and thus are more energy efficient.
Since there is no need of a complex chemical reaction, LED's use less energy (as it is based on the movement of electrons), more energy efficient and do not heat up as traditional CFL bulbs do. 80% of the energy of CFL is dissipated as heat. LED does not give similar results to CFL, in fact, it gives greater and better results. Though LED's are little pricey when compared to CFL, the annual energy savings and considering the replacement savings are much higher when you consider a long-term period. You may require replacing CFL very frequently and their energy consumption is also very high, but LED's power consumption is less and you need not replace them as frequently as you do with CFL.
Dr. V. Shashikanth