Monday, May 15, 2006

CFL follow-up

Perhaps I am exposing my energy hogging lifestyle when I say that until this week I've never installed/used a compact fluorescent lightbulb (in my house).

Following my recent post I've been investigating CFL prices. Prices are all over the place from $6 to $14.95 for a 25W CFL spring bulb = 100W incandescent. Because CFLs use 75% less energy than a normal bulb you can expect to save 0.6 cents per hour of use (assuming $0.08kWh electricity cost). So you recoup your $6 investment in 1000 hours, which is just under a year, assuming 20 hours of use per week. This is a worst case payback since I'm assuming the incandescent bulb is free. Obviously it will take longer if you pay more for your bulbs. The bulbs are supposed to last 8,000-10,000 hours. The $6 you save each year for the following 7-9 years is your dividend for investing in more efficient lights. Total savings ~ $50 per bulb over its life. Of course you save even more if you pay a higher electricity rate or use the light more than 20 hours/week (ok technically you just save it faster, but I'm assuming you re-invest your dividends :).

If the average house has 10 frequently used lights (20 hours+/week) replacing 'em all with CFLs can reduce your electricity bill by $50/yr.

If you had and replaced 30 frequently used 100W bulbs (or equivalent) with CFLs you get roughly the same annual utility bill savings as you might from installing 1kW of solar panels. Cost of 30 CFLs = $180 (30 x $6); cost of 1 kW solar panel = ~$5,000 + inverter and battery ~$5,000 (1kW system ~$10k). 50 times the payback of solar...and I think solar is awesome!

I've seen ~$4.50 a bulb in bulk--if they work as advertised I'll post my source :).


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