I’ve done everything I can to eliminate incandescent bulbs from my house, relying largely on CFLs. This has helped me dramatically reduce my power bills – but with some drawbacks. One is that outdoor CFLs in the porch light fixtures really do not work too well in the depths of a cold Minnesota winter. CFLs take a fairly long time to warm up to full brightness when it’s frigid outside.
But, I’ve found a good solution. Home Depot recently dropped the price of their 40W equivalent LED bulb to $10. It’s kind of a funky bulb; highly directional (top hemisphere) and not the warmest color. It’s fine, but not fantastic. But it’s perfect for a porchlight. If the fixture points down, the directionality doesn’t matter; you don’t need to illuminate the sky anyway. And light quality is not super important on a porch light.
Most importantly, it’s instant-on, even in the cold. At 8.6W, it’s 14% of the power draw of a 60W bulb. You could almost leave it on all night, and not feel too bad about it.
Porch lights are often left on for a long time; sometimes essentially forever. A 60W bulb burning 24/7 uses 44kWh/month; burning 12h a day uses 22kWh/month. I have neighbors who do this; I’m half tempted to drop off one of these bulbs on their porch some day!
Is $10 expensive for a bulb? Sure. But it should last essentially forever, and be honest – you were going to waste that money on something else, anyway, weren’t you!
Edit: Matthew Wilcox points out that these are “designed for indoor use only” – I guess I glossed over that part. :) I have them in mostly- and fully-enclosed fixtures. I guess we’ll see how they do!
Edit Nov 15, 2012: Over a year later, and they’re still fine, so I think as long as they’re in enclosed fixtures, outdoor use seems fine.