Customer Billing BPA strives for accurate and timely bill preparation and issuance. Below are some resources to help with understanding your bill. Billing Resources Billing and Payment Procedures These Billing and Payment Procedures apply to all Bonneville Power Administration (BPA) Power and Transmission Services’ customers. Monthly Generation System Peak (GSP) The GSP is the peak load (in MW) on the Federal System during a calendar month, determined by the largest hourly integrated demand produced from system generating plants in BPA's control area and scheduled imports for BPA's account from other control areas. Total Transmission System Load (TTSL) TTSL is an approximation of loading on any part of the BPA transmission system, based on federal and non-federal generation within the BPA control area, and interchange and wheeling onto the system. BPA Rates Power Rates Transmission Rates For questions regarding your bill or BPA’s billing practices, please call the Customer Billing Message Center at (503) 230-4211.