Will you save energy and electricity by switching the lights off, even if you’ll have to switch them on again in a little while?
I’ve recently written a couple of posts about lighting and energy efficiency – one about the most common types of light bulbs and one with more specific information about LED bulbs.
What these two posts don’t mention, though, is whether to leave the lights on or off when you’re leaving the room for a short period of time.
Turn the lights off, even if just for a short while
Now, I’m not suggesting you walk around in the dark and bump into stuff you can’t see. What I’m suggesting is that you only keep the lights on when they’re actually needed.
Well, duh, you might say, but the fact of the matter is that huge amounts of energy are wasted each year by lighting being left on when it’s not really needed. It might not seem like much if you leave the living room lights on for the night, but if enough people are doing it, the numbers add up to a high total.
Another thing you might say, is that you’ve heard that light bulbs and tubes consume a lot of energy right after they’re switched on. And that you’ll actually save energy if you leave the lights on if you’re just leaving the room for, say, 10 or 20 or 30 minutes.
This is principally true – all artificial light sources generate a small spike in consumption as they’re turned on. Realistically, though, the extra energy consumed during this spike is so small that it’s negligible for all intents and purposes.
“Well, that’s all very well for you to claim”, I hear you say – talkative today, aren’t you ;-D – ” but how can you be so sure?”
Well, at the risk of sounding a bit stupid: I know this because I’ve watched episode 69 of Mythbusters.
While primarily a fun and entertaining show – and not exactly high science – the Mythbusters crew are reasonably thorough in their methods, and always honest about the results of their experiments.
In the above mentioned episode, they measured the energy use of several types of light bulbs and tubes. As the different types were switched on, they used extra energy equivalent to being left on for a fraction of a second. The only exception was a fluorescent tube light, which used the energy equivalent to being left on for about 23 seconds.
Which means that if you’re leaving the room for more than just a few seconds, you will save energy if you switch the lights off.
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This post was tagged with: energy efficiency, energy saving, energy use, light bulbs, light sources, lighting
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But won’t constantly switching the light on and off wear the light bulbs and switches out faster?
Nah I saw that episode they tested that too. They found out the extra wear didn’t outweihg the energy you saved.
Yeah, what seanJK said
Unless you flick the light switch on and off every few seconds for hours at a time, the life of the light bulb and switch won’t be noticeably affected.