In my building I have a eight light fixtures that need to be lit 24 hours a day, 365 days a year. Some of these fixtures have a single socket, others have a dual socket.
Original Plan: Twelve 60 watt bulbs, $756 in electricity per year
Originally, we were running 60 watt incandescent bulbs. They provided more than enough light, but cost us a ton of money in electricity. Further, they had a lousy life, needing replacement several times per year - a lot of labor when you are paying a maintenance company.
More Efficient Plan: Twelve 13 watt CFL bulbs, $163 in electricity per year
About 5 years ago, we switched to 13 watt CFLs. These bulbs, on average, lasted nearly 3 years and saved us about 70%. We still had way more than enough light.
Current Plan: Eight 7 watt CFL bulbs, $60 in electricity per year
Two years ago we stepped up our game. We realized that we would get adequate light from 7 watt CFLs, and that multi-bulb fixtures only required a single bulb. That means four sockets went to zero watt bulbs! We used to pay 12 times more for lighting this space.
Other options and concerns:
Q. What about the quality of the light? Are 7 watt CFLs really bright enough? Don't they dim?
A. The quality of the light and the lumens produced is great for the space, even after years of service.
Q. What about CFL "start up" time?
A. Irrelevant in this case - the bulbs are almost never switched off.
Q. Why can you switch the bulbs off?
A. Given the use of the space, our insurance company requires 24 hour lighting.
Q. Why not go LED?
A. Perhaps someday, but the price point of LEDs wasn't good enough when we made the most recent change.
Q. Do your CFLs really last for so many years?
A. Absolutely, perhaps due to the lack of switching.
Q. Isn't it a waste to throw out otherwise working bulbs?
A. Yes, and we didn't. We use them in other locations where they aren't in use 24 x 365.
Q. How do you know how long your bulbs last?
A. We date them with a Sharpie when we install them.