Does Turning Off Lights Save Power

13July 2015

We have probably tried arguing with some friends and family as to whether or not turning off lights save power. Some of us believe it doesn’t matter if we leave it on or off, especially if we’re only going to turn it back on after a few hours. A credible show on The Discovery Channel, Mythbusters tested the effects on what happens when we turn off the lights. Do we in fact, conserve more energy if we turn off the lights after leaving the room?

The Myth

The myth was whether or not we really save money and conserve energy by turning off lights when leaving the room even just for a short period of time. Moreover, the question also needs to be answered as to whether or not the longevity of the light bulbs get reduced when the lights get turned on and off constantly. So what are we supposed to follow? Is it lights on, or is it lights off?

Hypothesis and Method

The main hypothesis of the experiment was that the “start up” burst of energy that happens every time we turn on the lights entails more energy consumption than just leaving the lights on. The method that the hosts from the Mythbusters did was to test different types of common light bulbs normally used at home or at industries. They tested different types.

Here’s what they found out:

Energy Usage During Steady State

  • Incandescent – 90 watts
  • Flourescent – 10 Watts
  • Compact Fluorescent – 10 Watts
  • Halogen – 70 Watts
  • Metal Halide – 60 Watts
  • LED – 1 Watts

How Long the Bulb Would Need to be Turned Off for It to be Worth the Energy Savings:

  • Incandescent – 0.36 seconds
  • Compact Fluorscent – 0.015 seconds
  • Halogen- .51 seconds
  • LED- 1.28 seconds
  • Fluorescent- 23.3 seconds


The results were not surprising. The fluorescent bulb was the one that had the largest start-up surge. It needed to remain turned off for 23 seconds before it becomes more energy-efficient to leave them off. Therefore, it is always better, that even when we only intend to leave the room for a little while, the lights need to be turned off. This conserves more energy, thus letting us save more money on energy bills. The myth was in fact, busted. For the longevity of the bulb, they also tested as to whether or not repeatedly turning on and turning off the lights shortens the life span of the bulb. What they did was to set up a timer and had the bulbs set to repeatedly turn on and off every 120 seconds. They had this experiment go on for 6 weeks. After the set period, the only light bulb that was still working was the LED. Aside from knowing as to whether or not, we can in fact save from turning off the lights every time we leave a room, they were also able to conclude that the bulbs would eventually burn out after five years of ordinary usage. LED would still be your best bet, though.

So now that you know this, think that every little thing that you do has an impact on energy conservation, and that you can definitely save on energy bill in the long run. A simple thing as turning off the lights when leaving the room can make a huge difference.

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