Phreak and BoiStoi are spot on - I'm running 24 CFLs from one outlet and have had absolutely no problems (I'm on my second grow).
Power consumption/lumen production are as follows:
Watts: 624
Amps: 9.36 Amps
Lumens produced: 38400
However, the lights, the timer, and one fan are the only thing on that circuit for a total power drain of under a 1,000 watts. This is well within safe limits of the 15 amp circuit that I'm on. My dishwasher, fridge, and stove (on another circuit) use a lot more amperage that these 24 cfls.
Make sure the cords wires are clean and in good condition (check on a regular bais) and use a fan to dissipate heat.
Having said this, I don't think I'll add any more lights on this circuit. My setup is just right for the small amount that I grow for personal consumption. I'm not growing anywhere near the volume you are, so I suspect you may have typical problems with too many plants and not enough light (elongated stems, loose and small bud production, etc).
If you're growing 45 plants, consider the amount of lumens available for each plant:
38,400 / 45 = 853.3
Don't think that's enough to give good results.