Until recently, most of us have used the incandescent lighting, which renders the color of objects more closely to that of natural light, in our homes. Fluorescent light was harsh and cold and typically used in offices.

Light is categorized by its color rendering index, or CRI for short, and its color temperature.  CRI is how a light source, a bulb, causes the color of an object to appear to our eye and how well variations in color and shade are duplicated in comparison to natural light.

The CRI number is a rating from 0 to 100, the higher the CRI number the better the color. An incandescent bulb has a CRI of 100. Fluorescent lights can have CRIs of anywhere from 50% to 99%.

Color temperature is expressed on the Kelvin scale (K) is the color appearance of the bulb and the light it produces.

The color temperature of lamps makes them visually “warm,” “neutral” or “cool” light sources. The lower the temperature (2700-3000K) , the warmer the source, yellow-red colors. The higher the temperature(5000K) the cooler the source, green-blue color range.

How this all applies to us when we go to buy light bulbs at Home Depot is that  we generally want light that will  give us the best color rendering, a high CRI number, usually with a neutral or warm color temperature, a lower Kelvin number.

Originally these parameters’ were only met by incandescent lighting, but that is not the case anymore. The compact fluorescent bulbs available today have CRI numbers and light quality that closely matches that of incandescent bulbs. Although compact fluorescent light (CFL) bulbs tend to be more expensive they convert electricity into light much more efficiently than incandescent. The lower energy cost of the CFL can offset the higher cost of the bulb. Compared to incandescent bulbs,  fluorescent bulbs use less power for the same amount of light and usually last longer

An article in Wikipedia states that  ” In the United States, a compact fluorescent light  can save over $30 dollars in electricity costs over the bulb’s life time compared to an incandescent bulb and save 2,000 times its own weight in green house gasses. ”

Many compact fluorescents are designed to replace incandescent bulbs and can fit into most existing fixtures.

A problem with compact fluorescents bulbs is that they are made with a small amount of mercury. This mercury  requires that they be disposed through a hazardous waste disposal program, they cannot be put in the regular trash.

Another type of light is the LED. The LED appears to be the bulb of the future. Although expensive LED bulbs can produce light that is comparable to incandescent.

LED (Light Emitting Diode) last longer that compact fluorescents, they use less energy than traditional bulbs and potentially, compact fluorescents. LED lights are made in all sizes and shapes. LEDs do not contain mercury so their disposal is not a problem.

An article in the New York Times quotes Charles F. Jerabek, the president and chief executive of Osram Sylvania, a unit of Siemans as stating “In the US 78 percent of the public is completely unaware that traditional light bulbs will be phased out in 2012.”

As we all konw that light bulbs should be more energy efficient, and incandescent bulbs will be a thing of the past.