How does a CFL bulb work?
Fluorescent light bulbs (including compact fluorescents) are more energy-efficient than regular bulbs because of the different method they use to produce light. Regular bulbs (also known as incandescent bulbs) create light by heating a filament inside the bulb; the heat makes the filament white-hot, producing the light that you see. A lot of the energy used to create the heat that lights an incandescent bulb is wasted. A fluorescent bulb, on the other hand, contains a gas that produces invisible ultraviolet light (UV) when the gas is excited by electricity. The UV light hits the white coating inside the fluorescent bulb and the coating changes it into light you can see. Because fluorescent bulbs don’t use heat to create light, they are far more energy-efficient than regular incandescent bulbs.

What’s the difference between a CFL bulb and a fluorescent bulb?
The primary difference is in size; compact fluorescent bulbs are made in special shapes (which require special technologies) to fit in standard household light sockets, like table lamps and ceiling fixtures. In addition, most compact fluorescent lamps have an “integral” ballast that is built into the light bulb, whereas most fluorescent tubes require a separate ballast independent of the bulb. Both types offer energy-efficient light.

What CFL bulb do I buy to replace a 60-, 75-, 100- or 150-watt regular bulb?
While a regular (incandescent) light bulb uses heat to produce light, a fluorescent bulb creates light using an entirely different method that is far more energy-efficient — in fact, 4-6 times more efficient. This means that you can buy a 15-watt compact fluorescent bulb that produces the same amount of light as a 60-watt regular incandescent bulb.

Don’t worry about the math, though — we make it easy for you to figure out which compact fluorescent bulb to buy by displaying the equivalent regular watts you’re used to prominently on the package. Just look for the wattage you would normally buy in a regular bulb. In case you’re curious, here are the watts needed by regular incandescent bulbs and compact fluorescent bulbs to produce the same amount of light.

How are the watts calculated?

  • 60 watt incandescent  =  15 watt compact fluorescent
  • 75 watt incandescent  =  20 watt compact fluorescent
  • 100 watt incandescent  =  26-29 watt compact fluorescent
  • 150 watt incandescent  =  38-42 watt compact fluorescent
  • 250-300 watt incandescent  =  55 watt compact fluorescent
* information reproduced from