Earlier quoted context omitted.
If demand substantially increases then more baseload capacity will likely be built. And it looks like New York peaks at around 4-5pm, with a drop off around 8-10pm. EVs will likely charge at night, meaning they won't have as much impact on the peak. Edit: source for load http://mis.nyiso.com/public/htm/isolf/20170705isolf.htm
They will have to setup some kind of timer or incentive to charge off peak, because otherwise, most cars are going to be plugged in around 5 to 6 right when people pull into their garage.
I'm not too familiar with ny in particular, but there are systems that allow for metering based on peak/off peak usage. Looks like coned allows this.