A Light Bulb Just Went Off in My Head

You know - it's amusing when you just realize that certain days weren't meant for work. For myself, those days are easy. They are generally the days that start with consonants. For the days that start with vowels, I'm all gung ho about doing work. Maybe it's just coincidence. But maybe something more sinister is at work.

So, during this day of non-work, I was just thinking about ways to save a buck, ways to help slow the increasing size of our ecological footprints. One thing came to mind quickly. Doing a little work around the house can really help. Things like making sure that your air filters are clean and closing the air vents to rooms that you don't use regularly are sort of obvious. Today, we also bought some of those window insulation kits that are really Saran Wrap and tape. Two of our windows got closed up, so that should help the cause, as well. But the one little change that I want to make a case for is with the long-life, energy-saver light bulbs.

Really, they're just like mini-flourescent light bulbs that fit into normal light fixtures. They're guaranteed to last 5 years. Let's take a peek into this:

If you buy a 3-pack of these bulbs out at Wal-Mart, you spend about $2.70 per bulb. A regular light bulb costs you about $0.20. So, right off the bat, you see that these bulbs cost 13.5 times more than regular light bulbs. Can you ever justify this purchase?

Well, first of all, you see that you'll have this bulb for at least 5 years. For them to make this guarantee, you have to figure that the average bulb will last something like 7 years (if you're interested in the stats behind this outrageous claim, I'm just ballparking a break-even figure with a 95% confidence interval, an exponential distribution for defects, and 20% rate of return on defective parts). Based on casual observation, it seems that normal light bulbs wear out every 5 or 6 months. Let's just say that it's 6 months. This means you're looking at using 10 - 14 regular bulbs for each of these fancy mini-flourescent bulbs. Let's just use 10 bulbs, since that's what guaranteed. That means that this is the same as buying $2.00 worth of light bulbs. So, you're getting close. But you have more of an upfront cost - you're paying for everything up front. If you have a simple 5% discount yield (too lazy to use the rate), you could save another $.35 or so in the long run.

How long will it take for you to save $.90 using this light bulb? We'll use a 100W light bulb as our reference point. Let's say that each light bulb is on for 2 hours a days. Most of the lights in my apartment are on more, some are on less, but let's keep it conservative. Anyway, that's .2KWH per day, or about 6 KWH per month. Right now, I'm averaging about $0.074/KWH on my energy bill (https://www2.ameren.com/ACMSContent/Rates/Rates_ipel13rtSC2.pdf ). So, I spend about $0.444 per month for each light bulb. Over the course of a year, that's $5.32 per year. Now, what's interesting is the number of light bulbs you have in an apartment. A quick count in my little place reveals 24 light bulbs. That's a cost of $127.68 per year with normal light bulbs. Now, there's about a 4 to 1 ratio for the actual watts used by these energy saver light bulbs. Basically, this is a 75% discount in power cots for switching to the energy saver, long life bulbs. This adds up to $4.30 per light bulb, or about $95 per year for the entire apartment.

And keep in mind, this is using a very conservative estimate. The bulb cost could be as much as $1 off. And the energy cost could be off by as much as a factor of 2.5 (depending on how many hours you ordinarily leave your lights on). So really, you could be saving as much as $10.75 per year for each light bulb by making the change.

So, we see that you save a few bucks by making the change. What does this do for our ecological footprint? The EPA suggests that 1 KWH is equal to burning 1 pound of coal, or the production of 2 pounds of carbon dioxide (http://www.cogreenpower.org/EnvBen.htm ). Each light bulb runs at a 75% lower wattage than normal light bulbs. So, if a 100W normal bulb is on for 2 hours a day for 365 days, that's 36.5KWH that is used on that light bulb. Our energy saver light bulbs would only actually use 9.125KWH, for a savings of27.375KWH per year. If I were to switch 20 bulbs over to these energy saver bulbs, that would be 547KWH saved. That would be like removing the pollution from 1400 mile drive , or making the round trip from Urbana to downtown Chicago 5 times (http://www.mapquest.com ).

Interesting, huh?

Don't worry. We'll be back to talking about drinking, gambling, women, sports, and the brutal nature of the PhD program soon enough.

-Chairman