Today's Energy Outlook
California ISO (Independent System Operator) operates the California high voltage electrical grid as well as the real-time market that operates in seven states. In addition, the ISO manages the wholesale energy market (energy is a commodity) through which competition establishes the wholesale price for energy. The high voltage (220 and 500 kilovolt) grid extends from power plants to substations (the utilities are responsible for the distribution grid which delivers stepped down electricity to homes and businesses). The ISO’s primary mission is reliably operate the system to prevent and avoid power interruptions as well as ensure competitive access to the transmission system. If necessary, the ISO can order utilities implement rotating power outages to protect grid equipment or to reduce the amount of load on the system if demand outpaces the system ability to generate electricity.
CAISO or Cal-ISO or just ISO has an extensive information database that is published on their website. Today's Outlook is a 24 hour set of charts that displays data on near real-time and day-ahead predicted electrical load. The page is automatically updated every few minutes. The charts display the actual electrical demand now, and day ahead and one hour ahead forecasts, and available resources. Below this chart is another chart displaying the status of renewable electrical resources, e.g., solar, wind, geothermal, biomass, biogas, and small hydro. You can see how these renewables vary during the day. In addition there is information on system Alerts, Warnings, and Emergencies.
Electric utilities, like Palo Alto use long-term fixed price contracts to purchase electricity. Palo Alto has no power plants and so must purchase electricity for their customer needs. To satisfy the imbalance between last minute demand and supply, utilities will buy power in the real-time market called Energy Imbalance Market; it is also called a spot market. ISO uses a term 'congestion'. Congestion occurs when a power line doesn’t have the capacity to carry all the power wanting to use it, kind of like freeway congestion. To manage congestion, grid operators have to find additional transmission paths to deliver that energy. Wholesale prices can vary depending on grid conditions and factors such as the cost of natural gas. From what I can tell by observation, normal pricing is around $20-$30 per megawatt during fall and spring and $40-$50 per megawatt during the summer. But sometimes it can be less than zero during times of excess generation (when we are generating more power than can be consumed). At other times it can be greater than $200/MW when congestion is high or there is a scarcity of energy. This open market pricing information is public and available online. Market Price Maps display the actual cost to produce and delivery energy from specific points on the transmission grid called nodes where power plants connect to the system. Each node is represented by a colored dot. The dot color changes with the price. The Web page displays Day-Ahead Market LMPs (locational marginal price), and real-time Fifteen-Minute Market and Five-Minute LMPs. You can even check out other system grids outside California which are part of the western Energy Imbalance Market, a real-time market where utilities buy the last little bit of power needed to meet real-time demand. The web page is updated automatically every few minutes.