As we talked about in our primer on light bulb tech, not all types of light bulbs are created equally, especially when it comes to efficiency (or lack thereof). But it’s one thing to talk about the best types of bulbs, but it’s another thing to consider how best to use them. Many of us have been trained to turn the lights off every time we walk out of a room. While this is usually the best option, believe it or not, this is not always the most energy efficient choice–it takes energy to create bulbs in the first place, and in some cases, shortening the lifespan of your light bulbs will ultimately cost more energy than you save by always turning the lights off.
Read on to learn more!
Incandescent Lights
Okay, in this case, the rule applies. Incandescent lights use energy at such a ferocious rate that they should be turned off whenever possible.
But really, if you actually still have an incandescent light bulb in your house, it’s time to donate it to a museum. To put their inefficiency in perspective: the amount of energy that one 100 watt bulb consumes in an hour could power an iPhone for more than a month. Seriously.
Compact Fluorescent Lights (CFLs)
This is where it starts to get a little tricky. The lifespan of CFLs is significantly affected by how often it’s switched off and on. The sudden transition from being off to on is kind of jolting, so to speak, for CFLs.
This can be hard to picture, so here’s a metaphorical visual: imagine standing on a skateboard and holding one end of a rope, with the other end being tied to the bumper of a car. The car starts and takes off quickly, peeling out and laying down rubber as it goes. When the slack runs out, you are suddenly accelerated, and during that short period, it would feel like your shoulder was being pulled out of its socket (as it might well be in that scenario). That momentary acceleration process is the nasty part. Once your speed has caught up to that of the car’s, it would be a much more comfortable ride–there would be tension on the rope, but it would be manageable.
That’s a bit like how it is with CFLs when they’re powered on. Once they’re running, they’re fine. But in that first moment when they’re firing up, it’s a bit traumatic. The more times that a CFL is switched on and off, the more that trauma builds up, until it ultimately causes the bulb to fail in one way or another. (However, contrary to popular belief, it does not require minutes’ or hours’ worth of electricity to initially start up a light bulb. The energy consumed in the startup process would only keep the CFL on for, at maximum, about five seconds.)
The reason all of this matters is because CFLs are efficient enough that the energy you save in switching them off can be offset by the shortening of their lifespan. As we said earlier, manufacturing light bulbs uses a fair chunk of energy, so killing your light bulbs faster than necessary means that energy is being wasted.
So, here’s the rule of thumb: 15 minutes. If you’re not going to need to the light for more than 15 minutes, go ahead and shut it off. If you’re going to need the light on within the next quarter hour, then go ahead and leave it on.
LEDs
We’ve sung the praises of LED bulbs in a previous blog post. There’s a lot to love about them, aside from their relatively high cost. Well, there’s one more reason to love LEDs: you can switch them off and on as much as you like without affecting their lifespan. You could stand there all day switching an LED light off and on again; the light switch would break before the bulb would.
Additionally, similar to CFLs, it takes very little additional power to turn on an LED bulb. Ironically, all of this means that you should use LED lights like you would incandescent lights: turn them off whenever you aren’t using them, even if it’s just for a minute or two.
