Friday, November 29, 2013

Five year test of CFL bulbs

Five years ago, I wanted to do an experiment. The government passed a law that phases out incandescent light bulbs in favor of more efficient bulbs. They claimed at the time that the more efficient bulbs would save a homeowner money through lower energy costs, despite the fact that the newer bulbs were much more expensive. They claimed that this was due to the longer life of the lower energy bulbs.

So I set out to look at this issue, because I am a big geek like that.

There are 46 light bulbs required in my home. I replaced 25 of them with compact fluorescent bulbs.

19 of them were of the spiral variety. They currently cost $1.50 each. At the time that I originally bought them, they were more than $8 each. 4 of them burned out and had to be replaced during the five year test period. At today's prices, this means that the 19 bulbs cost $34.50 over the five year test period.

6 of them were PAR lamps that were used as spotlights in the track lighting that illuminates the kitchen. These bulbs were quite expensive, costing $12 each at the time. They currently cost $4 apiece. Three of them burned out, for a total cost in today's prices of $36.

During that same period, four of the remaining 21 incandescent bulbs had to be replaced. These bulbs cost 50 cents each, with a total cost of $12.50.

The total cost for fluorescent bulbs is $2.82 for each  of the bulbs, factoring in the costs of replacement bulbs. They are not as long lived as the government claims, with about a third of them failing over the five year period.
The total cost for incandescent bulbs is 60 cents each.

The CFL bulbs use 18 watts of energy each. The incandescent bulbs use 60 watts. The price I pay for electricity is 12 cents per kilowatt hour.

This means that the difference in energy costs for outfitting my entire home with CFL bulbs would require me to run my every one of my 46 light fixtures for 3 hours per day each in order to break even. Of course, no one does that.

Conclusion

The only way that this becomes cost effective is if you only replace the lights in your home that are most frequently used. Closet and bathroom lights, which are used far less than lights in the living and bedrooms, are simply not used enough to justify the added costs of CFL bulbs.

Also, the costs and performance of the PAR type CFL bulbs make them a poor choice.

3 comments:

Graybeard said...

It would be nice if they left you with that choice, instead of mandating that incandescents be taken off the market.

I experimented with them in a few places and never saw dramatic (or, really, even noticeable) improvements in bulb life. They seem to fail fairly quickly when they're mounted with the base above the curly tube. My guess is they're a marginal design and the extra few degrees of heat the electronics gets from being above the bulb makes them fail sooner.

Divemedic said...

That makes sense. Being track lighting, the PAR lamp fixtures are mounted base up, and the light fixtures enclose the bulbs rather tightly, keeping the heat in.

Anonymous said...

Don't forget that a single CFL bulb also contains enough mercury that if it breaks would, in theory, be an OSHA violation. It would require evacuation and decontamination of the building as well. So, what are they doing to the ground water and environment when you throw them away?