CFL analysis

This post is a little outdated, as CFLs have been replaced by LEDs, but the ideas apply, I believe.

Ok, read something that got me to thinking...it was about the cost savings of installing CFLs.
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(From Five Cent Nickel's pf blog)
"Now let’s work through the math so we can come up with some hard numbers.

Incandescent assumptions:
100 watt incandescent bulb
8 hours/day
365 days/year

100 watts corresponds to 0.1 kilowatts. At 10 hours/day that works out to:

0.1 kW * 8 hours/day * 365 days = 292 kWh

I just checked our latest power bill, and we are currently paying $0.108/kWh for electricity, so that one incandescent bulb would consume $31.54 worth of electricity per year.

Compact fluorescent assumptions:
26 watt compact fluorescent bulb
8 hours/day
365 days/year

Doing the same math as above, we have:

0.026 kW * 8 hours/day * 365 days = 75.9 kWh

At the rate for electricity, that works out to $8.20 per year — a savings of $23.34 per year just for switching out one light bulb. And that’s considering just the cost of electricity.

Given that most CFLs are rated to last an estimated 10x longer than incandescent lights, you’ll come out even further ahead if you can get them for less than 10x the price of an incandescent bulb. Since CFL pricing has come down dramatically in recent years, you’ll actually come out way ahead."
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I actually installed about ten CFLs in my house in various locations as the incandescents burned out, and I really haven't noticed any cost savings on my electricity bill.

So, I don't dispute that, for a given quantity of light over a given period of time, CFLs will use less energy, which is probably a good thing.

However, I don't think the theoretical cost savings will ever really be realized for most households.

In the first place, who leaves the lights on in their house 8 hours a day? In a commercial building, I can see that there would be significant energy savings, but at home? Most of us get up in the morning, turn on a few lights for whatever time it takes us to get ready, then turn them all off, and leave for work. When I come home from work, it's still lights out, and I don't turn on any lights until around 9 pm (in the summer time), at which point I've got another hour or so before I go to sleep, anyway. We turn off all lights except one on the nightstand, so on a good day, I've only got maybe 16 to 32 light-hours (kinda like man-hours) for the entire house. I suppose one could actually keep a journal of how many lights are on in the house, for how long each day, and actually make predictions based on that of more realistic cost savings from installing CFLs.

Second, who uses 100 watt bulbs in the house? Most light fixtures rated for home use say 60w maximum. Using 5C's methodology:
60 W incandescent
.06kW*8 hours/day*365 days = 175 kWh
14 W CFL
.014*8 hours/day*365 days = 41 kWh

that's a savings of 134 kWh at $.108/kWh = $14.42 per year per bulb replaced (THAT OPERATES 8 HOURS PER DAY).

From a financial standpoint, it only makes sense to replace "high use" bulbs with CFLs, if you're interested in ROI.

Third, as I mentioned before, I've seen little to no reduction in my electricity bills from the CFLs. Did I somehow purchase bogus CFLs? Or, is it just that the bulk of my electricity use is from other things. I suspect the latter. I have a refrigerator that runs 24 hours a day, an electric dryer that we run three or four 45 minute loads in each week, an electric dishwasher that runs 2 or three loads a week, an electric oven used to cook our food at least a few times each week, an electric fan in my heater/air conditioner that runs almost constantly, except in the spring and fall, an electric motor in the heat pump for the AC, computers, printers, routers, modems, coffee machine, can opener, toaster, microwave...you get the picture? CFL usage just isn't gonna cut it, in my opinion.

If you want to save the planet, you better learn to live without any of the modern conveniences, the light bill ain't the half of it!