nightime power consumption would rise and power generation would have to dialed up to keep up with it. Wouldn't we be right back where we started?

There are so many consumers that power consumption varies continuously, in smooth curves. But power production goes up in discrete fits and starts, as more generating capacity is brought on and off line.

Also, even if generating capacity is on line, power output need not necessarily be high. A generator with no load on it can be turned easily with only a small amount of maintenance power from fossil, hydro or nuclear. As users come on line, current draw in the generators increases and there is time for the power sources to be ramped up gradually. It's only during those peak moments, (7 AM weekday mornings when everyone turns on their appliances at once) that sometimes demand can outstip supply if the utility is not ready for the extra load.

During periods of low demand (late at night) the utility still has to have standby capacity on line (lit off but at low output) ready to absorb extra demand should it be required. There has to be a safety factor padded in. That will still be the case if people are charging their cars while they sleep.