Doesn't every gallon of gas I don't burn make your gas cheaper?
I realize that it is an exercise in futility to discuss electricity usage and the grid with most people but maybe you're the exception? So here goes: 
Peak power usage is expensive. Power used during off peaks can be very cheap and sometimes relieves the utility of paying fees associated with not using enough power. Some areas pay users to use power during hours of low use. My car is scheduled to only charge during the period from 11:45 PM to 5 AM. In the end, that can make all grid users have cheaper power.
The typical data center spiel usually states they will find their own source of power but use the grid to deliver it. They will need to pay for massive grid updates but if and when they fold up, guess who will be on the hook to finish paying for those improvements?