30 May 2018
Estimating the lifespan of a light bulb
When I started shifting from incandescent to LED bulbs, I was curious about the claims of long-term cost-savings. So when I replaced some in my office, I made a note of the date.
Yesterday one of the above bulbs started to die (recurrent and annoying blinking). My notes showed an installation date of February 2017, which meant it had lasted about 15 calendar months. The claim on the package (UR corner) is for 9.1 years of life. Was I being misled?
I tracked down some source data for the newer model of this bulb and found that it is rated for "11,000 hours of life," or "10 years." That calculates to 1100 hours = 1 year, or an average usage of 3 hours per day as the standard. Other sources online use the same standard "Estimated yearly energy costs assume 3 hours of daily use." Apparently that is an industry standard.
My office bulbs are on about 15 hours/day, so the 9.1 years projected life at 3 hours/day would translate to 22 months at my usage, and the 15-month life of my bulb was a bit brief, but at a unit cost of $2 each in multipacks, it's hard to complain.