Switch to LEDs!
Seriously, though, LEDs might make the grade next year. Expensive though (figure on $500/fixture to do what a $50 PAR 64 can does). I'm running 16 LED cans on one 15-amp circuit. They're second generation (23 W each) and not very bright, but figure LEDs probably consume 1/3 the power of incandescent WHEN PRODUCING THE SAME AMOUNT OF LIGHT, so you could probably get it down to one 20-amp cord if you were willing to pay the money.
Cheers,
Randy Hyde
Hoping I'm not continuing to derail the thread farther...
I've done some work researching LED Pars this year for my own use. The current crop of 10,000 lux fixtures compete easily with 500 watt Par 64s and on saturated gel colors can compete well with 575 watt Source 4 fixtures. The fixture I ended up with, the Chauvet SlimPar Pro RGBA, draws 80 watts per fixture, which means you can hang 30 of them on a 20A circuit.
Comparing efficiency of LEDs to incandescent fixtures is slightly more complicated than just comparing input wattage of both fixtures.
A 575 watt S4 Par with a blue gel on it at full brightness will draw 575 watts.
My Chauvet RGBA with only the blue channels on at full brightness draws as I recall about 23 watts (I measured it, but don't have the numbers in front of me). The Chauvet takes only about 4% of the power that the S4 Par does in this case for the same output, which is 25
TIMES as efficient.
However, an ungelled 575 watt S4 Par still draws 575 watts, but now puts out enough lumens that you need at least 4 of my Chauvets (probably more) to get anywhere close to the white output of the S4 Par, or 320 watts, for much poorer quality white (yes I'm aware that there are other fixtures that can do white better and more efficently).
The big reason to go LED for color wash is that you replace multiple fixtures with a single LED fixture. It usually takes 3 conventionals to provide a mixing palette pointed at one location on stage. These three fixtures, the cabling and three dimming channels are replaced by one fixture, much less trucking space, and less setup and teardown time. Factoring this in and assuming you don't already have a large sunk cost of conventional fixtures, LEDs start becoming awful darn cost effective.
They also go very far in helping solve the problem of unqualified people wanting to tie in to heavy power, as your whole light show may now take less than 1 circuit.
Street price for the Chauvet is ~$320. Depending on your needs for a fixture, it may not be "Pro" enough, but it works for me.
