Since fluorescent lamps use less power to supply the same amount of light as an incandescent lamp, they decrease energy consumption and the environmental effects of electric power generation. Where electricity is largely produced from burning fossil fuels, the saving reduces emission of greenhouse and other pollutants.

While CFLs require more energy in manufacturing than incandescent lamps, this is offset by the fact that they last longer and use less energy than equivalent incandescent lamps during their lifespan.

Energy saving 

 The chart shows the energy usage for different types of light bulbs operating at different light outputs.

 Points lower on the graph correspond to lower energy use.

If indoor incandescent lamps are replaced by CFLs, the heat produced by the building's lighting system will be reduced.

At times when the building requires both heating and lighting, the building's central heating system will then supply the   heat.

If the building requires both illumination and cooling,  then CFLs will use less electricity themselves and will also reduce the load on the cooling system compared to incandescent lamps. This results in two concurrent savings in electrical power.

 

Mercury emissions

 

Mercury use of compact fluorescent lamp vs. incandescent lamp if powered by electricity generated completely from coal.

 

Mercury has been used in a variety of consumer products because it exhibits properties of both a metal and a liquid at room temperature, it is a good conductor of electricity, and it reacts precisely to temperature and pressure changes.

 

CFLs, like all fluorescent lamps, contain small amounts of mercury as vapor inside the glass tubing, averaging 4.0 mg per bulb ,and it is a concern for landfills and waste incinerators where the mercury from lamps is released and contributes to air and water pollution. We, LOYAL, now manufacture CFLs with only 1.0 mg or less than 1.5 mg of mercury per bulb.

 

 

Lifespan

The average rated life of a CFL is between 8 and 15 times that of incandescents. CFLs typically have a rated lifespan of between 6,000 and 15,000 hours, whereas incandescent lamps are usually manufactured to have a lifespan of 750 hours or 1,000 hours.

The lifetime of any lamp depends on many factors including operating voltage, manufacturing defects, exposure to voltage spikes, mechanical shock, frequency of cycling on and off, lamp orientation and ambient operating temperature, among other factors. The life of a CFL is significantly shorter if it is only turned on for a few minutes at a time: In the case of a 5-minute on/off cycle the lifespan of a CFL can be up to 85% shorter, reducing its lifespan to the level of an incandescent lamp.

Note:  http://en.wikipedia.org/wiki/Compact_fluorescent_lamp