Incandescent is not used for growing. What you want to know is how effective CFL's are for growing, and apparently they can be used, but I prefer linear fluorescents. Incandescent is mainly a heat source, with very little light, and cannot be used for growing.
The wattage equivalent is given on the box or package, but that is the wrong question. Sativa.

Well I'm not going to decide I know what you want to know, so here's what I know:

CFL's generally used about 1/4th to 1/5th the wattage of an incandescent lightbulb that puts out the same amount of brightness. For example, the 26w CFL commonly found in practically every lighting section of every store is roughly equivalent in the total light output of a 100w incandescent.

I have a 105w CFL that's supposed to be as bright as a 500w incandescent, but I've never seen or heard of a regular style bulb that big. I can tell you, though, that this CFL is about the size of a football and not something you want to look directly at.

But it is correct that an incandescent light isn't any good for growing plants. They don't put out light in the right spectrum for the plants to use (plants can't use just any frequency of light to grow), and incandescents do put out a ton more heat than light. If you want to keep something hot as hell, put an incandescent nearby. If you want to spend as much as possible on your electric bill, use them in your house's lights.

There's only a few disadvantages to CFLs. First, they've got mercury in them so you really don't want one to break (very toxic) and it's irresponsible to simply throw them away when they burn out. You're supposed to send them to the proper facility for recycling and safe disposal. Also, they don't work in dimmer switches unless you get a special (expensive) type of bulb.

But that's about it. They're great for growing plants indoors and they save a ton of electricity. They're also very cool (not burning hot) so you can put them very close to plants, where they'll be most effective.

Another important thing to look at when buying CFLs is the "color temperature". For growing you'll want either 6500k or 2700k (commonly called "daylight" and "soft white", respectively). The 6500k is great for vegetative (leafy) growth and the 2700k is more commonly used to encourage reproductive (flower) growth. I use mainly 6500k with a few 2700k's tossed in the mix.