Well, right now many of the Independant System Operators (ISO's) have specific markets for frequency support which are theoretically separate from the market fo

Well, right now many of the Independant System Operators (ISO's) have specific markets for frequency support which are theoretically separate from the market for energy supply. So as distributed renewable dump-as-much-as-available style generation gets added to the grid, in principle the price for frequency support increases. In the same vein, distributed energy storage works very well for frequency support, which can drive the price for that service downwards. That still leaves the wires themselves. At the residential level, you typically pay a flat connection fee for the wires (and distribution and maintenance thereof). Commercial sites pay a Demand Charge for their peak total power consumption at any time during the billing period. So that's how the interconnect infrastructure gets paid for - the commercial demand and residential interconnect charges.