When compact fluorescent lights came on the market, I was skeptical, and I was dismayed by their high cost. I really had a hard time convincing myself to spend over $8 for one 200-watt-equivalent bulb, so I decided to figure out whether the purported energy saving would translate into actual savings in real life.
The first CFL I bought listed an energy usage of 40 watts to generate the lumens of a 200 watt standard (750-hour) bulb. We pay 9-10c per KWH. I installed that bulb in an office lamp, and rather than try to track the on-time of the lamp with precision, just estimated that the lamp was in use for five hours per day.
Bottom line: The bulb would pay for itself if it lasted for 100 days. That was over two years ago. And the packaging I saved when I got it says it can last "up to 5 years." No matter. The bulb has easily paid for itself - many times over.
If/when I have another house, I'd also like to investigate the possibility of lighting it with LEDs.
Photo via.