Environmental column: Lights and lies (sort of)
Published: Monday, September 23, 2013
Updated: Monday, September 23, 2013 22:09
You know those new-ish style light bulbs that advertise massive monthly savings on your home energy bills? I’m talking about the Compact Fluorescent Lamp, also known as CFL or spiral bulbs and the even newer Light Emitting Diode bulbs. The manufacturers are lying to you. Well, more precisely, they are misleading you by great oversimplification. I’m not arguing a slight calculation error or some nit-picky difference in assumption, but a failure to look at a home’s energy budget in a holistic manner.
On average, the manufacturer’s claimed savings are true when you use their reasonable assumptions—the key term here being “on average.” Many people don’t realize, however, that your energy savings from these bulbs will vary greatly across seasons. Here’s my central point: in summer, you can expect to save much more than the advertised amounts by switching to newer bulbs, while in winter you net savings will be closer to zero.
One might ask, “So, mister, how is it you can predict home energy use patterns without even stepping foot in my home?”
The answer is heat. Ever since Thomas Edison’s first electric light bulb roughly 130 years ago, incandescent lights (as the old ones are called) have been extremely inefficient. These bulbs convert far less than 10 percent of electricity into light with the remaining 90-plus percent wasted and turned immediately into heat. Not only are these bulbs very inefficient, but they also consume lots of electricity. For example, a 75-watt incandescent bulb may be needed to light a modest room, while a LED can do the same task at about 14 watts. For comparison, an iPhone and laptop may draw 3 watts and 30 watts, respectively under heavy loads.
Don’t believe me? Try to touch one of those old style light bulbs while it is on, and you will quickly realize the bulb gets very hot. Now, touch a CFL or LED bulb giving off a similar amount of light and you will notice it runs much cooler. In fact, CFL and LED bulbs are about four to five times more efficient than incandescent bulbs, meaning they produce similar amounts of light with a fraction of the energy.
So how does this all fit together? You see, in winter we expend a great deal of energy to warm our living places. (This is not true of all places on earth, but in temperate climates like ours, it certainly is.) Similarly, during summer, we expend a great deal of energy to cool our house. The “inefficiency” of old bulbs is given off as lots of extra heat which warms the house. So while the old style bulbs use lots of electricity, they end up not increasing energy bills much in winter because they help offset heating requirements. Simply stated, the waste heat is useful in winter. In the summer, however, the opposite is true. Not only is the waste heat not useful, but the cooling system has to work much harder to remove the excess heat.
So what to do with this new knowledge? First, it is very important to change incandescent bulbs in the warmer months, and far less important in the colder months. As most people already know, CFLs have their own set of drawbacks. CFLs contain trace amounts of mercury and are not instant-on. In addition, many people dislike the light these bulbs give off. High-quality LED bulbs, on the other hand, represent the best of both worlds, but are expensive at about $10 or more each. They have an energy efficiency on par or greater than CFL bulbs, are instant-on and produce a pleasant light. Furthermore, they have a lifespan of decades that is unrivaled by either the other bulbs. Beginning in 2014, however, most incandescent bulbs will be phased out anyway, so choices will be constrained.
In conclusion, if you really pine for the familiar glow of an old-style bulb in the cooler months, enjoy them knowing that your electricity bill will barely change. In the warmer months, however, that old bulb will work double duty to nudge your bill even higher; once at the light fixture itself, and again at the air conditioner.