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Supply and Demand

Supply and Demand is a graphical representation of the ERCOT system’s current power supply (capacity) and demand using Real-Time data, as well as projected power supply (capacity) and demand from hourly forecasts and seasonal forecasts. 

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Current Day

Demand

The graph’s turquoise line represents the demand (the amount of power used).

Committed Capacity

The graph’s solid dark purple line represents the committed capacity (the amount of power available from generating units that were on-line or providing operating reserves).

··· Demand Forecast

The dotted turquoise line represents the forecasted demand.

··· Committed Capacity Forecast 

The dark purple dotted line represents the forecasted committed capacity. Committed capacity amounts are based on generating units' Current Operating Plans and change over time based on generating units’ start-up and shut-down plans, as well as forecasted wind and solar generation output.

- - Available Capacity 

The light purple dashed line represents the forecasted available capacity, which is comprised of:

  • the forecasted committed capacity,
  • current committed capacity that is planning to go off-line but is available to remain on-line, and
  • additional capacity available to come on-line, if committed at present. (The available capacity in each future hour takes into account the start-up time of each generating unit, therefore it typically increases further out in time.)


6-Day Forecast

··· Demand Forecast

The dotted turquoise line represents the forecasted demand.

- - Available Seasonal Capacity 

The burgundy dashed line represents the forecasted available seasonal capacity, which is comprised of:

  • the forecasted available capacity of non-renewable generators based on seasonal capacity ratings without regard to the operating plans of these units, minus any known outages or derates of these units, and
  • the forecasted wind and solar generation output.


*Note: The 6-Day Forecast graph should only be used as a relative indication of future system conditions. Due to uncertainties associated with the longer-term nature of the forecasts used, both the Available Seasonal Capacity and Demand Forecast may adjust significantly as the Operating Day approaches.

*Note: Capacity available from demand response programs is not reflected in the Current Day and the 6-Day Forecast graphs unless these programs have been deployed.

These values are all provided in megawatts (MW). 1 MW of electricity can power about 200 Texas homes during periods of peak demand.