Turn off all lights when not in a room

Recently I started posting a more in depth look at each of the frugal tips. Over the next few weeks I will publish the frugal tips that I have collected. Please note that not every tip will work for everyone. Chose as many of the tips that will work with you and your family and start implementing them. Today we will proceed with Tip #6 Turn off all lights when not in a room.

This one we all have heard for years. There was even a time when people would claim it would cost more to turn the light off and turn it back on if they were gone only a couple of minutes. But today we are going to look at the facts. What is true and what isn't?

First, the cost effectiveness of when to turn off lights depends on the type of lights.

Incandescent Lighting

Incandescent lights (or bulbs) should be turned off whenever they are not needed. Nearly all types of incandescent light bulbs are fairly inexpensive to produce and are relatively inefficient. Only about 10%–15% of the electricity that incandescent lights consume results in light—the rest is turned into heat. Turning the light(s) off will keep a room cooler, an extra benefit in the summer. Therefore, the value of the energy saved by not having the lights on will be far greater than the cost of having to replace the bulb.
- EnergySavers.gov

It absolutely doesn't affect the lamp life of an incandescent bulb very much at all. So it makes sense to always turn them off when you a leave room, even if it's only for a few minutes.

Fluorescent Lighting

The cost effectiveness of turning fluorescent lights off to conserve energy is a bit more complicated. For most areas of the United States, a general rule-of-thumb for when to turn off a fluorescent light is if you leave a room for more than 15 minutes, it is probably more cost effective to turn the light off. Or in other words, if you leave the room for only up to 15 minutes, it will generally be more cost effective to leave the light(s) on. In areas where electric rates are high and/or during peak demand periods, this period may be as low as 5 minutes.

Fluorescent lights are more expensive to buy, and their operating life is more affected by the number of times they are switched on and off, relative to incandescent lights. Therefore, it is a cost trade-off between saving energy and money by turning a light off "frequently" and having to replace the bulbs "more" frequently. This is because the reduction in usable lamp life due to frequent on/off switching will probably be greater than the benefit of extending the useful life of the bulb from reduced use. By frequent we mean turning the light off and on many times during the day.

It is a popularly held belief that fluorescent lights use a "lot" of energy to get started, and thus it is better not to turn them off for "short" periods. There is an increase in power demand when a light is switched on, and the exact amount of this increase depends on the type of ballast and lamp. The ballast provides an initial high voltage for starting the lamp and regulates the lamp current during operation. There are three basic types of ballasts: magnetic (of which there are energy-efficient and not so energy-efficient types), cathode-disconnect, and electronic. All types can operate two or more lamps simultaneously. There are three main methods that are used in a lamp's ballast to start the lamp: preheat, rapid-start, and instant-start.

In any case, the relatively higher "inrush" current required lasts for half a cycle, or 1/120th of a second. The amount of electricity consumed to supply the inrush current is equal to a few seconds or less of normal light operation. Turning off fluorescent lights for more than 5 seconds will save more energy than will be consumed in turning them back on again. Therefore, the real issue is the value of the electricity saved by turning the light off relative to the cost of relamping a fixture. This in turn determines the shortest cost-effective period for turning off a fluorescent light.
- EnergySavers.gov

Yahoo Green helps explain it this way,

Compact fluorescent light bulbs, on the other hand, are a somewhat different story. Flicking them on and off repeatedly will affect how long they last, although, Rubinstein points out that the impact is minimal for most households.

How much flicking on and off is too much? The general consensus is that it's best to turn off CFLs when you are leaving for 15 minutes or longer. In fact, Energy Star recommends installing fluorescent bulbs in fixtures that are used for at least 15 minutes at time. So it doesn't make sense to use them in places where you'd need to switch them on and off constantly.

The rule of thumb is a little different when you're at the office, according to Rubinstein. Turn out fluorescent lighting when you're leaving for at least 5 minutes. The reason? Full-size fluorescent systems aren't as sensitive to frequent cycling as CFLs and won't impact the life of the bulb as much.
- Yahoo! Green

LED Lighting

I searched and searched but could not find anything on the web that talked about how this strategy affected LED bulbs. Perhaps because they are still to new. Still I would like to find a definitive answer for these types of bulbs as well.

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