Does turning off a light really save energy?

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Currently, the trend in lighting fixtures is predominantly towards energy-efficient LED fixtures, which consume approximately 1/4 of the electricity compared to traditional lighting fixtures. Additionally, LED fixtures do not suffer from the high initial power consumption issue experienced by early fluorescent lamps (energy-saving bulbs). It is advised that when leaving an area unused, it is beneficial to turn off the lights promptly to achieve energy-saving effects.
For those who still use energy-saving bulbs or traditional fluorescent lamps, it is important to note that the initial inrush current may be approximately 5 to 40 times higher than the normal operating current, varying according to different impedance designs of various products. Assuming a 40W fluorescent lamps with a total power consumption of about 50W (including the ballast consumption of 10W), the inrush current during startup can be estimated to be 5 to 40 times higher, resulting in a power increase of 5 to 40 times as well. Considering a startup time of 0.4 seconds (the maximum duration for typical electronic preheating), the electricity consumed during startup is approximately 0.000028 to 0.000224 kw.hr, equivalent to the power consumption of lighting the lamp for 2~16 seconds.
Frequent switching of fluorescent lamps naturally reduces their lifespan, leading to increased replacement costs for the tubes. Considering both the cost savings from turning off the lights and the expenses related to replacing tubes due to frequent switching, it is generally advisable that if an area remains unoccupied for more than 3 minutes, promptly turning off the lights will indeed result in energy conservation.

Update: 2023-08-09
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