Incandescents: Wait for Burn Out?

Back on my latest Energy Efficient Lighting post, Andy left a comment that really got me thinking. His comment was, “…and [I] will likely buy more [CFLs] when my other bulbs burn out.”

This raised the question for me: Is it more efficient to wait until your existing incandescent bulbs burn out, or is it better to toss them in the trash and upgrade to CFLs immediately? This calls for some analysis (something that Jim over at Bargaineering would like). Here’s what I’ve come up with:

We’re currently paying $.15 / KWH for electricity.

Burning a 100-watt bulb for 1000 hours uses 100,000 WHs or 100 KWHs of energy. At $0.15/KWH, that costs me $15.00.

If I switch to a 23-watt CFL (100 watt equivalent output), I use 23% of the energy over that same 1000 hrs, or 23KWH. Again, at $0.15/KWH, that would only cost $3.45, a savings of $11.55.

For $11.55, I could buy a whole pack of CFL bulbs. But, that really doesn’t factor into the analysis, because I would have to buy the CFL bulbs at some point anyway (when the other bulbs burn out). So this really isn’t a difference. The small amount of interest I might earn if I didn’t buy the CFLs for another 6 months would surely be negligable.

You might ask, what if the incandescent only has 2 hours of life left? Even then, the numbers say to make the switch early.

The verdict: Throw out those incandescents and make the switch to CFLs immediately.

So the real question is: why is this so hard to do? I think it’s because most of us feel like it is wrong to throw out a working bulb, but we fail to recognize that we’re throwing away energy every day we don’t make the switch. I know that was my feeling. Putting a working incandescent in the trash just feels wrong. So I didn’t, I put them in a box and saved them for who-knows-what. Home improvement shouldn’t involve such moral dilemmas!

What do you think? Will you throw out your incandescents before their time?