Compact Fluorescent “Bulbs” February 9, 2006Posted by techandother in Free Money, Home Tech, My Projects.
When I first moved into my townhouse, I couldn’ figure out why my electric bill was so bad. I had attributed 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
70W x 50 bulbs = 3500 watts
3000 watts x 43.5 hours per week = 152,250 watt/hours = 152.25 kilowatt/hours
152.25 kW/hours per week * 4 weeks = 609 kW/hours per month
609 kW/hours per month * 8.275 cents per kW/hour = $50.39 per month
$43 per month! Just for the 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. CF 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. CF’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 CF 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. Ow.
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.
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 month
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 CF bulbs, of course.
In fact, I then replaced every bulb in my entire house with CF, 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.
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)
FREE MONEY: $31.37/month for 50 replacements
(about 63 cents per bulb replaced)
*Combine these savings with a seven-day thermostat and save $54.11 per month! (about $650 per year!)