[edit] Energy efficiency


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.


For a given light output, CFLs use between one fifth and one third of the power of equivalent incandescent lamps.[19] Since lighting accounted for approximately 9% of household electricity usage in the United States in 2001,[20] widespread use of CFLs could save as much as 7% of total US household usage.
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.

[edit] Efficacy and efficiency

For more details on this topic, see Luminous efficacy.
A typical CFL is in the range of 17 to 21% efficient at converting electric power to radiant power.[21] Because the eye's sensitivity changes with the wavelength, however, the output of lamps is more commonly measured in lumens, a measure that accounts for the effect of the source's spectrum on the eye. The luminous efficacy of CFL sources is typically 60 to 72 lumens per watt, versus 8 to 17 lm/W for incandescent lamps.[22]

Put HPS/MH up there see it go even lower.