The cost effectiveness of when to turn off lights depends on the type of bulb and the cost of electricity. The type of light bulb you use is important for several reasons. All light bulbs have a nominal or rated operating life, which is affected by how many times they are turned on and off. The more often they are switched on and off, the lower their operating life. (courtesy of the energy.gov)
Incandescent lights should be turned off whenever they are not needed, because they are the least efficient type of lighting. 90% of the energy they use is given off as heat, and only about 10% results in light. Turning lights off will also keep a room cooler, an extra benefit in the summer.
While halogens are more efficient than traditional incandescent bulbs, they use the same technology and are far less efficient than CFLs and LEDs. Therefore, it is best to turn these lights off whenever they are not needed.
Since CFLs are already very efficient, the cost effectiveness of turning CFLs off to conserve energy is a bit more complicated:
– If you will be out of a room for 15 minutes or less, leave it on.
– If you will be out of a room for more than 15 minutes, turn it off.
The operating life of a CFL is more affected by the number of times they are switched on and off. You can generally extend the life of a CFL bulb more by switching it on and off less frequently than if you simply use it less.
The operating life of a light emitting diode (LED) is unaffected by turning it on and off. While lifetime is reduced for fluorescent lamps the more often they are switched on and off, there is no negative effect on LED lifetime. This characteristic gives LEDs several distinct advantages when it comes to operations. For example, LEDs have an advantage when used in conjunction with occupancy sensors that rely on on-off operation. Also, in contrast to traditional technologies, LEDs turn on at full brightness almost instantly, with no delay.