At our office the main panel has 3 hot legs coming in. There's one 200A
master breaker at the top of the panel, then all the usual 15A, 20A
breakers for various office circuits below.

If 120V * 200A = 24,000W, would I need a 24KW 3-phase generator, or would
I need 24KW * 3 = 72KW generator (eek!) ... or is my math completely off?

I understand there's more to generator sizing for air conditioning, motor
loads, etc., just trying to get a really rough idea of what kind of beast
I would be looking at if the entire panel could be powered off the genny.
In other words a $5000 - $10,000 beast, or a $15,000 - $20,000 beast. g

-- Paul

Just to follow up - the big mama safety switch by the service entrance says
"200 Amp 240 Volt"

Inside the circuit breaker panel it says "200 amp, 3 phase, 4 wire". There
are 3 hot wires coming in, plus the neutral. The schematic inside the panel
shows each of the 3 hot legs going to alternating rows of breakers. Leg 1 =
row 1, 4, etc., Leg 2 = row 2, 5, etc., Leg 3 = row 3, 6, etc.

But yes, of course, I'm going to be talking to a pro installer about this...
I see that I'll have to dial it down to powering just the essentials.

-- Paul