Even when that isn't the case, they say, the current system for reserving space on the grid from day to day is slow and cumbersome and must change to meet new demands. The network began developing only 50 years ago, when utilities decided to share power, rather than each build enough facilities to meet their peak power needs independently. To this day, the transmission lines are owned by investor-owned utilities and some public power utilities. Establishing ISOs and improving transmission-reservation practices have been surprisingly difficult. But the system is deceptively complex.
Power is moved onto the grid by generators or power producers and pulled off it to serve customers.
It's like a lake with water pouring in from several sources and pouring out in other places. Individual electrons moving through the grid are difficult to track, although computer programs and meters are used to mimic actual power flow on the grid for accounting purposes. That task falls to line-owning utilities or, in some places, ISOs. Use of the transmission grid is priced separately from the cost of power. Consumers, too, may soon see the distribution costs broken out from power costs on residential bills as deregulation moves to the retail level.