It has nothing to do with what he's asking. He's not asking us to sit down and run the numbers on exactly how much current draw he's going to have from 4kw, he's asking what kind of electrical he'll need to support it. Regardless of how much power we're actually running, we all refer to our systems by what their nominal (max) power is. My amp is rated at 3kw, does it actually output 3kw all the time? Hell no, but when talking about what electrical I'll need I didn't sit down and try and figure out exactly what kind of power I'd see from it, I just upgraded the electrical to handle 3kw.
There's no need for you to be such a critical dick, he's just asking how many batt's he needs, no need to flame him.