About "Ask the Energy Expert"
Craig Muccio runs FPL's Conservation Research & Development Program and crunches the numbers to figure out how you can save by managing your energy use.
Your questions on energy-related topics can be submitted anytime to our Ask the Energy Expert blog. Just click here to submit your question, and if chosen, it will be answered here
I was once told that it takes more energy to turn a light on and off than it does to just leave it on for 10 minutes or so. Is this true?
There is a little extra electricity involved in turning a light on due to more power needed during startup. However, the amount used is more like leaving the light on for a couple of seconds of normal light operation. Therefore, we recommend turning off a light whenever it is not needed.
One thing that you may want to consider, though, is the lifespan of the bulb itself. The cost effectiveness of turning off lights depends on the type of bulb. All bulbs have an average operating life, which depending on the bulb type could be affected by how many times they are turned on and off.
Incandescent lights should be turned off whenever they are not needed, because they are the least efficient type of lighting. Ninety percent of the energy they use is given off as heat, and only about 10 percent results in light.
CFL AND OTHER FLUORESCENT LIGHTING
For CFL and other fluorescent lighting, the answer depends on the frequency and length of time you turn your lights on and off. The operating life of CFL and fluorescent bulbs is affected by the number of times they are switched on and off. You can generally extend the life of these bulbs by switching them on and off less frequently. You’ll save energy by turning the light off, so you’ll need to determine if the savings outweighs the cost of replacing the light bulb if it fails early due to frequent switching.
LEDs are a good option for lights that are switched on and off a lot because the operating life of an LED is unaffected by turning it on and off. It’s always best to turn off LED lights whenever they are not needed.
For more information about the different lighting options for your home, please read
my previous blog post on this topic.