Incandescent lamps in the hand v. compact fluorescents in the bush...?

Question

All right, this is a question that I've wondered about for a while but never devoted the brain cells to answering...

Say you already have a stockpile of incandescent lamps (i.e. light bulbs) in the basement. Is it more cost efficient in the long run to burn your current stockpile of incandescents or go out and purchase compact fluorescent lamps? (Assume that the fixtures in question are used less than two hours per day.)

Also, please answer as to winter usage v. summer usage. (Meaning, during winter a 100 watt incandescent lamp will help to heat your house more than the equivalent light output of a compact fluorescent), plus the electricity rate in winter tends to be lower than summer.

Thank you in advance for your well-thought-out and mathematically and engineering sound responses. Please also take into account future value v. present value of money. And no, this is not a homework problem. Only a mind as demented as mine could come up with this.

Answer 1

Properly done, a furnace is a more efficient way of heating a space than an incandescent light bulb. So moving energy for heating from the light bulb to the furnace improves efficiency both of the lighting and the heating.
Since you probably can't get your purchase cost back out of the incandescent bulbs [IBs], from an individuals view, it would be better to use them. But it should be possible to figure costs to make it rational and how much you would have to get for selling the bulbs.
FCB's are available in a box of 6 from GE at Walmart for under $11 right now, so call them $2 each. "60 watt" FCB's use 13 watts and last about 10,000 hours. The already paid for 60 watt IBs last about 1000 hours (there are longer life versions, but they are dimmer and use more power) although both hour ratings are based on 8 hours on - the more time on each time turned on the longer a bulb lasts - turning on produces surge damage.
Electricity in Texas currently costs about 13 cents a kWh. So a CFB uses 13 / 1000 * 10000 *.13 $16.90 in its life or $18.90 with purchase. Ten incandescents to run 10,000 hours use $39. So using the incandescents blows off $21.10 a socket and you could pay someone $21 for each ten bulbs to haul them away and be ahead of the game and ANY money someone paid you would be a gain on your cash flow.

Answer 2

Look at it this way. If you spend $2 to replace a 75 W bulb with a 20W CFL, your savings in a year is around $4, assuming 2 hours a day at $.10/kwh. How many other investments will double your money in a year? I occasionally see the CFLs on sale for $1 each, too.

As far as the heating value of incandescents, if you have electric heat, it's a wash; you'll just the use that much more electricity for heating. Even if this cut your savings to $2 a year, you double your money in 2 years; still a good deal. If you heat with something other than electricity you save more because electricity is the most expensive form of heat.

Answer 3

Do you know the phrase "Throwing good money after bad"? To use incandescent lamps just because you already have them is just that. Especially since you can buy compact fluorescents for 25 cents a piece. At least where I live. The electricity company is subsidizing them because giving people a compact fluorescent for almost free is cheaper for them than building another power plant.

I have spent approx. $2000 on new appliances this year and calculated that I am getting an annualized return of seven or eight percent. That is four percent better than putting the money on the bank. And it helps to slow down global warming. Our Prius, by the way, returns about seven percent on its investment and saves 300 gallons of gas a year. Not bad, is it?