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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.

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

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).

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.

The light purple dotted 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.)

Because the forecasted values of both available and committed capacity are based on the next hour’s end, and the historic value of the committed capacity is continuously updated, the graph may appear to show an abrupt change that will actually occur over the next 1-2 hours. This is not a cause for concern.   

Note: Capacity available from demand response programs is not reflected in this graph 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.