The Indian power system is a large network with an installed capacity of 140GW. It is unique in that it is the only network which allows the operating frequency to vary over a band from 0.5 Hz to -1.0 Hz from the nominal 50 Hz. The pricing for power purchased is a function of the operating frequency following a commercial mechanism called availability based tariff. Since the network consists of several states which are each commercially independent, an elaborate metering system is required at the interconnecting 400 kV grid. Since 2004, 461 special energy meters with 0.2 class accuracy have been erected across the network. They provide online information about key network parameters in addition providing the data for commercial transactions. We show several examples of the utility of this measuring system with regard to scheduling plants in the network, planning and control studies. We propose a grid transaction index that would help assess the state of the network and the performance of various state's dispatchers. All discussions are based on the data of Tamil Nadu Electricity Board (TNEB), a utility in the Southern region.