That's wild! What all are you running?? I'm going to guess there are either multiple metal halides or seriously heavy duty pumps/heaters involved. My setup at peak (all pumps, powerheads, lights, heaters, etc. at their absolute highest power draw they're rated for) is less than 7 amps. Not sure what the actual current draw is though. Sounds like you're about to have 90 amps of circuitry installed!!
When I was designing my enclosure, I did some research to find what people with smart plugs typically see as their actual current draw for their tanks. The typical current draw for an average reef tank seems to sit in the 2.5-3A range. I saw only 2 responses using above 5A, both were using multiple metal halide lights.
Absolute highest response I found was a guy running about 25 amps, with 3 250W metal halides, 4 60" T5s, huge 3.5A return pump, 800W
9A heater, & more. This was for a 375 gallon SPS tank.
I guess what I'm getting at, is unless you're running a fish store, or the equivalent, in your house.... 90A is *major* overkill. The 4 circuits at 60A miiiight be necessary if you've got a crazy setup & a lot of other power-hungry electronics on the same circuit as well. I'd be curious to hear what all you've got on that one circuit & why he thinks 60A would be the minimum. I'm not a professional electrician, so I'm not saying he's wrong... but for a figure like that, there'd better be a good reason