Scientific American had an article on the costs of light bulbs1. I wanted to figure out a way to fairly compare the rough lifecycle costs of the bulbs to the consumer. I figured the best way to do that would be to determine the cost per an operating lux-hour.
We’re going to figure out the cost to buy and operate lights that emits 1600 lumens for 20000 hours given that energy costs
2:
Traditional Incandescent
Cost of energy:
Cost of bulbs:
Total Cost:
You can do the same math for the rest of the bulbs (substituting the proper numbers in) to get a chart that looks like this:
Traditional Incandescent |
Halogen Incandescent |
Compact Fluorescent (CFL) |
LED | |
---|---|---|---|---|
Watts (W) | 100 | 77 | 23 | 20 |
Lumens (lm) | 1600 | 1600 | 1600 | 1600 |
Cost/bulb | $0.37 | $1.59 | $2.23 | $45 |
Life span (hours) | 750 | 1000 | 10000 | 20000 |
W/lm | 0.0625 | 0.0481 | 0.0144 | 0.0125 |
$/(lm-h) | 5.313E-06 | 4.091E-06 | 1.222E-06 | 1.063E-06 |
Cost to run | $170.00 | $130.90 | $39.10 | $34.00 |
$/h | 0.493E-04 | 1.590E-04 | 2.230E-04 | 2.250E-04 |
Cost to buy | $9.87 | $31.80 | $4.46 | $45.00 |
Total cost | $179.87 | $162.70 | $43.56 | $79.00 |
Here’s the thing I found amazing: there’s a big push to implement LEDs, probably because of the ‘cool’ factor. However, they don’t save that much more energy over CFL — about 13% — and they cost almost twice as much to operate right now. Manufacturers are going to have to have to drop the cost of LED lights a lot in order to make a change worth it…or the government will have to ban mercury in lights3.
Graphic by George Retseck and Jen Christiansen
Sources: U.S. Department of Energy and Efficacy calculations based on currently available bulbs (traditional, halogen and compact fluorescent); SWITCH LIGHTING (led)
How to Buy a Better Lightbulb, John Matson, Scientific American, January 6, 2012 ↩
CFLs contain about 4mg of Mg, per Energy Star ↩