Ah, that's the disconnect. Typically the electric company is the local provider here. Some provide service all the way from generating stations, some broker power contracts from neighboring generating stations but you typically only have one company to buy power from and they are the ones that build the infrastructure to the home. My utility lets you buy power from partnered solar farms, that solar farm would not have any idea what my home size is, but the utility that physically runs the power cables to my house sure does.