Question:
Does it really take more energy to turn a light bulb on than to run it for 30 minutes?
dracnath
2005-12-30 08:09:51 UTC
As a child, after 2 minutes of turning on and off a light, I distinctly remember having been told by my mother, that it takes more energy to turn on a light bulb, that it does to run it for 30 minutes. Terrified of the environmental ramifications I never did that again. However I'm wondering if it is true for a standard old light bulb. I seriously doubt it. However what about a halogen, florescent, or even LED? Any thoughts?
Two answers:
Chris
2005-12-30 14:47:35 UTC
Not true... generally. Standard bulbs may have a reduced life span as result of constant on-and-off because of the constant temperature fluctuation of the filament. As for energy consumption, the initial warm-up is almost instant such that it "essentially" does not use any more energy to turn on. Halogen bulbs are similar to standard bulbs except the bulb is pressurized with halogen gas for more light output. LEDs are not affected either way. As for florescent bulbs, they do require a ballast to initially heat the gas up which DOES take a little more energy to start up than run - but definitely not 30 minutes worth of running.



Your air conditioner is a different story. It requires a surge of amperage to start up and uses far less energy to simply run. I still wouldn’t say it compares to 30 minutes worth of constant running though - maybe 10 or so. Your AC turning on an off constantly will not only produce a higher energy bill but will wear out the electrical components faster.
tatian15
2005-12-30 08:59:47 UTC
How bad a current surge bulbs draw when turned on



It is fairly well known that a cold light bulb filament has less resistance than a hot one. Therefore, a light bulb draws excessive current until the filament warms up.



Since the filament can draw more than ten times as much current as usual when it is cold, some people are concerned about excessive energy consumption from turning on light bulbs.



The degree of this phenomenon has become a matter of urban folklore. However, the filament warms up very rapidly. The amount of energy consumed to warm up a cold filament is less than it would consume in one second of normal operation.


This content was originally posted on Y! Answers, a Q&A website that shut down in 2021.
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