Revenue cycle and exposure of electricity power vendors

Hello,

Does anyone know what is the revenue cycle the electrical energy providers undergo from the moment they buy the energy from the power stations to the moment they sell it to the final customer?

I would like to understand what is the liabilities they have when in the electrical power business and to understand if they are forced to pay in advance with respect to the moment they receive the revenue from the sale of the energy 

I am particularly interested to know what is the time that elapses from the moment they purchase the energy when they bid to the moment they are paid for that energy from the final user.

Thanks a lot

Gianni