Geek Money: Switching over to Compact Fluorescents

Project Name: Compact Fluorescent Replacement x 50

Initial Cost: $250
Recurring cost: $250 every 8000 hours, plus $14.92/month
(new bulbs and energy costs, bulbs will probably be cheaper by then)
Time involved: 90 minutes
(Get the bulbs, remove old, install new)
Time to pay off initial investment: about 8 months
(varies, the more you use them, the faster they pay off)

GEEK MONEY: $31.37/month for every 50 replacements
(about 63 cents per bulb replaced)

Raining MoneyWhen I first moved into my townhouse, I couldn’ figure out why my electric bill was so bad. I had attributed it to summertime and the air conditioning, but soon noticed something else…
The fire hazard

A light bulb had burned out, and while replacing it, I noticed that the bulb was a 70-watt unit, and the recessed lighting receptacle was only rated for 60W. This can be a fire hazard, so I checked a few other bulbs – all 70 watts! A few were even 100 watts, with the labels on the recessed lighting turning brown from the heat!

This was bad. I counted how many 60W bulbs I would need. For my small house, I needed about 50. Ouch. “But wait”, I thought, “If I have 50 bulbs at 60W each, and I pay ComEd 8.275 cents per kilowatt/hour, I can figure out how much these bulbs are costing me.”

A kilowatt/hour is a measurement of how much energy is flowing to your house. It represents 1000 watts being used in an hour. So let’s say I have my lights on for about 43.5 hours per week… (when I’m home during the week, and 8 hours on the weekend)
Excel to the rescue

60W x 50 bulbs = 3000 watts
3000 watts x 43.5 hours per week = 130,500 watt/hours = 130.5 kilowatt/hours
130.5 kW/hours per week * 4 weeks = 522 kW/hours per month
522 kW/hours per month * 8.275 cents per kW/hour = $50.39 43.20 per month

$50 per month! Just for these lights! That doesn’t count for computers, bathroom lights, fridge, TV, AC, etc.

OK, so settling down, I could just go and buy 50 60W bulbs. This would cost me about $1.00 for a 4-pack from Home Depot, or about $12.50. It would also save me $7.19 per month, making my bill about $43 instead of $50. I would pay off the new bulbs in 1.7 months, and save $7 per month after that. Pretty weak, especially since 60W bulbs usually need to be replaced about every 400-800 hours (on average), which means every 9-18 weeks.

However, Home depot also sells Compact Fluorescent bulbs. compact fluorescent bulbs are basically like the big, long bulbs you see at work or in the grocery store. They are filled with a gas that glows when a small amount of electricity is applied to it. They use hardly any energy, and are more efficient than a regular bulb, which uses a lot of electricity to heat a small wire. compact fluorescent’s are different than the big, long ones, in that someone made the tubes very narrow and curled them all into the shape of a normal light bulb. Sometimes there is even a glass covering over the fluorescent tubing to make it look more “normal”.

The good thing about the compact fluorescent bulbs is that you can get a 6-pack that costs less than $30 these days, with each bulb putting out as much light as a 60W bulb, while only using 13 watts each. In addition, these bulbs are rated for anywhere between 8000 to 10,000+ hours.

The bad part is that each bulb costs about $5, instead of 25 cents.

OK, so let’s see what would be better over the course of 8000 hours of use, the equivalent of 3.8 years of use for me.

Regular bulbs
Cost for bulbs: 50 bulbs, each replaced (on average) every 800 hours = $125
Cost of electricity for 8000 hours: $1,986.00
Total cost: $2111, or about $46.29 per monthcompact fluorescent bulbs
Cost for bulbs: 50 bulbs, lasts for 8000 hours = $250
Cost of electricity for 8000 hours: $430.30
Total cost: $680.30, or about $14.92 per month


So what do I do? Replace the 70W bulbs with 60W bulbs, or bite the $250 bullet and go with the 13W bulbs that output as uch as 60W bulbs?

The compact fluorescent bulbs, of course.

In fact, I then replaced every bulb in my entire house with compact fluorescent, including bathrooms, lamps, outside lights, even the garage light. Total cost was around $325, no small amount, to be sure. But then again, saving $50 per month on 70+ bulbs…pretty sweet.

4 thoughts on “Geek Money: Switching over to Compact Fluorescents”

  1. we call those energy savers, use them outside the house as well as in hard to reach places. great, and save a lot of money too

  2. The numbers are fine IF you are using that much power. Are you really using all those light bulbs ? I looked at my own use and averaged 3-4 lights on at once . Most of the lights here are rarely used. Also there are 1000 hr light bulbs that I use in hard to reach places. I really question your use of lights. Sometimes we can delude ourselves to justify anything. You also fail to mention that the bulbs contain mercury, a hazardous waste here. They cannot be sent to any dump I know of.
    Sorry no sale, just turn the lights you have off and save 100%

  3. Ideally, a light turned off saves the most money, and helps the environment to the largest degree. Unfortunately, not everyone can sit in the dark. If a person lives alone, I can see them saving money because they don’t need a large portion of the house lit. Unfortunately, to do the most good, an initiative like this can’t afford to inconvenience people; the end user needs to continue receiving the same service they are used to, and hopefully the technology can lower the cost of that service over the long run.

    However, in the case of this posting, IF you need a significant portion of your home lit, then these are the way to go, at least until LED lighting becomes available.

    Something else to consider if your home is well lit is that a large portion (think about 95%) of an incandescent bulb’s energy is transformed into heat. Depending on your usage, this may account for not only the cost of the lit bulbs, but also the energy required to keep the home cooled in the summer.

    I agree that CFLs shouldn’t end up in a dump. That’s why there are recycling programs available. Ironically, if you are concerned about mercury, CFLs are your best bet. The largest source of mercury pollution comes from coal plants in the US, and lowering energy usage prevents mercury pollution to a degree greater than the small amount actually contained in the bulbs. Furthermore, recycling CFLs recover most, if not all, of the mercury contained within. We have not yet found a way to do so with our power generation plants.

    Here’s the info from the US EPA:

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