Rodeo Joe , Apr 05, 2013; 05:56 p.m.
CFL lamps are about 4 times more efficient than incandescent filament bulbs. So an 85W CFL will give out around the same amount of light as a 350W tungsten lamp. But, that doesn't take into account the higher colour temperature of the CFL, and because it's a closer match to daylight it'll give a higher effective exposure to daylight-balanced film or a digital sensor. You'll probably find there's little difference in the actual exposure settings needed between an 85W CFL and a 500W/3200K tugsten lamp. Your studio will certainly be cooler and your portrait sitters feel more comfortable with CFLs.
Another (lower cost) alternative might be to swap to Tungsten-Halogen lamps. These are about 30% more efficient than standard tungsten bulbs, so a 350W T-H would give an almost identical output to a 500W "conventional" lightbulb. Some types now have a double glass envelope that overcomes the drawback of being sensitive to handling and finger grease.
Personally, though, I had my fill of hot lights many years ago and re-equipped with studio flash as soon as I could afford it. Never looked back.