Quote:
Originally Posted by woj
that's a pretty naive way of comparing costs... 
the author overlooks one minor detail that 50,000 hours assuming lets say 8 hours per day the bulb is lit, is 17 years !!! (and that's a pretty generous assumption, most likely average light bulb is probably lit half that)
and cost of electricity is actually closer to 10 cents per kwh, not 20 that was used in the calculations, at least that's what it is here in Illinois...
so you invest 10x more upfront to save 40% ($60 saving / $160) over 17 years...
I can't really be bothered to calculate it out, but my guess is that you would be better off just buying cheaper bulbs and investing the difference elsewhere... |
A quickie way of estimating investment growth is that normally an investment will double about every seven years. Yes, the last three years have sucked, but historically doubling every seven years is about right.
So we take our $2,400 we're spending on LEDs and put in in any decent no-load mutual fund. In 17 years we'll have about $14,000, plus or minus an Obama.
According to the math in the article, IF all your your lights are on for eights hours a day, and if a bulb really lasts seventeen years, and if you're paying double the going rate for electricity, LED it would save you $14,000. Investing would give you $14,000. So that breaks even if all of your lights are on all day.
Looking around my house, I have TWO lightbulbs on, not every light in the house. Counting the four bulbs in each bathroom, the ones in the closets, the one in the attic, etc, I probably have about 30 bulbs, but only two on. Let's say I average two bulbs at a time for fifteen hours a day. That's thirty bulb hours per day. Divide that by thirty bulbs and that's an average of one hour hour per day per bulb.
The author said spending $2,400 would save me $14,000 at 8 hours per day. Since the average bulb is on only one hour, we divide the savings by eight.
That's $1,750 saved on the electric bill by spending $2400. So LEDs put us in hole by $650.
Investing the money would have earned us $1,400. The investment is a better choice by $2,050. In other words, once you include tbe opportunity cost, with LEDs you lose $2050.
If the author wanted to promote LED and also have a bit of intellectual honesty, he would have said that in your desk lamp or any light that DOES run for eight hours a day, LEDs won't cost you much in the long run. In the attic or closet, you're just throwing away $35 if you buy LED. The difference in your electric bill will be about two cents after you spend $35 per bulb.