EIA counts U.S. electricity generation in different ways
At EIA, we publish U.S. electricity net generation from two different perspectives:
- We publish monthly net generation for every grid-connected power plant located in the United States with at least 1 megawatt (MW) of nameplate capacity in our Electric Power Monthly, Electric Power Annual, and Power Plant Operations detailed data files.
- We publish hourly net generation reported by local and regional balancing authorities in the Lower 48 states in our Hourly Electric Grid Monitor.
The two sets of reports reflect different generating units, so adding up net generation from the Hourly Electric Grid Monitor from each hour of a month or year will not match the net generation published in our Electric Power Monthly or Electric Power Annual.
Why doesn’t hourly generation data match monthly or annual generation data in EIA reports?
EIA’s Hourly Electric Grid Monitor only captures generating units that are managed by a balancing authority and generating units with operations visible to a balancing authority. A balancing authority is an entity that is responsible for balancing electricity supply and demand at a regional or local level. Balancing authorities include organizations such as the regional California Independent System Operator (CAISO) and Southwest Power Pool as well as authorities in cities and municipalities within states.
Balancing authorities typically do not meter generators on the distribution system, meaning large-scale resources and small-scale distributed resources such as rooftop solar photovoltaic systems often aren’t included in the hourly generation they report.
How can we tell which power plants are reflected in each set of EIA reports?
We have long published a list of all electric generators reflected in our Electric Power Monthly and Electric Power Annual in both detailed data files and in our Preliminary Monthly Electric Generator Inventory.
We recently published a new list of the electric generators reflected in the Hourly Electric Grid Monitor. This dataset, compiled from responses to a new survey we launched last year, only includes generators metered by balancing authorities.
Which set of EIA reports provides the more comprehensive view of generation?
EIA’s Electric Power Monthly and Electric Power Annual provide a more comprehensive view of net generation in the United States because they reflect all generation from grid-connected power plants located in the United States with at least 1 MW of nameplate capacity.
For example, the New York Independent System Operator does not meter generation from most of the solar facilities in New York state, so our Hourly Electric Grid Monitor does not reflect the solar generation from these non-metered facilities within New York. However, the electricity generated by these utility-scale solar facilities is reflected in our Electric Power Monthly and Electric Power Annual.
However, some balancing authorities report generation that is not reflected in our Electric Power Monthly and Electric Power Annual.
For example, CAISO is a balancing authority that covers most of California. Because CAISO also meters four power plants physically located in Mexico, the electricity generation that CAISO reports to us and which is reflected in our Hourly Electric Grid Monitor includes the output of those four power plants in Mexico. However, in our Electric Power Monthly and Electric Power Annual, we only report generation from power plants located in the United States, so the generation from these four facilities in Mexico is excluded.
Is it possible to reconcile the two sets of EIA reports?
Analysts can identify information about the characteristics of generators reflected in the Hourly Electric Grid Monitor by cross-referencing the EIA plant codes and generator IDs with the same codes used in our other datasets. Our Annual Electric Generator Report detailed data files and our Power Plant Operations Report detailed data files both report generator-level details using these EIA plant codes and generator IDs.
Principal contributors: Jonathan DeVilbiss, M. Tyson Brown
Tags: electricity, generation, map, consumption/demand